Dick Graham increased the average age of United's squad at the start of the 1970s with the summer signings of ex-England international Ray Crawford, Brian Garvey, John Kurila, Mick Mahon and Brian Owen.
The Football League, despite the protests of the pools companies, re-introduced permission to play Friday night football.
Colchester arranged ten games for Friday kick offs but it would be the FA Cup that drew worldwide attention.
United disposed of non-League Ringmer via a Crawford hat trick in round one and then completed a Cup double over new boys Cambridge, having already secured a 5-0 win over the 'other' U's in the League Cup.
Both Roy Massey and Owen incurred career ending injuries forcing Graham to sign Brian Lewis and Dave Simmons.
Colchester knocked out non-League Barnet at Underhill in the third round only to be drawn away to Rochdale. Trailing 3-1 with just five minutes left, United staged a remarkable comeback to earn a replay.
With the knowledge of the Fifth Round draw having been made, United trounced hapless Dale by 5-0 to earn a home tie with mighty Leeds on February 13th 1971.
Leeds were top of the League and boasted ten internationals in their side, Colchester were eighth in the Fourth Division.
Nobody gave the U's a chance but they raced into a 3-0 lead, in front of a 16,000 Layer Road crowd, with goals from Crawford (2) and Simmons before Leeds generated something of a comeback to finally lose 3-2.
The result was sensational as was the fact that United were in the FA Cup Quarter Finals.
Sixth Round opponents Everton did their homework and Graham's 'Granddads Army' finally succumbed to the tune of 5-0 in front of 53,028 at Goodison Park.
While United finished sixth, just two points off promotion - they simply had too many fixtures to complete in rapid succession as a result of the cup run.
The U's goalscoring prowess however did qualify them for the 1971/2 pre-season Watney Cup. The competition was open to the two highest scoring teams from each division that had not won promotion.
U's saw off Luton and Carlisle at Layer Road to reach the final against West Bromwich Albion, at The Hawthorns.
A thrilling encounter saw the tie level at 4-4 after extra time leading to Colchester's first-ever penalty shoot-out. Albion missed two and U's one leaving youngster Phil Bloss to slam hone the decisive winning spot-kick.
After the exploits of the previous season's cup run and now Watney Cup success, United were firm favourites for promotion.
But with an ageing side and a club debt amounting to over £21,000 (£400,000 today based on average earnings index) and with the floodlighting requiring urgent maintenance work, Graham turned full circle and introduced youth to United's side.
Steve Leslie, Steve Foley, Lindsay Smith, Micky Cook and John McLaughlin were just some who came in during the rapid break up of Granddad's Army.
All would become regulars in United's side but youth alone was not sufficient for United to maintain a serious promotion bid and they finished 1971/2 in eleventh place, nine points adrift of promotion.
When the club held its AGM in September 1972, Graham was so incensed of the questioning, by a shareholder, of his team and tactics that he tendered his resignation.
The shareholder, it was alleged, had won his five shares in a raffle but his actions put United in chaos.
A month later an unknown Jim Smith was appointed manager. He had led Boston United to the Northern Premier League title and one of his first signings was Boston striker Bobby Svarc for £6,000 but United had just six points from 13 games and sat bottom of the entire League.
Smith's arrival gave an initial boost and he actually collected the Manager of the Month award for lifting United off the bottom.
It was not to be and United had to go to the Football League to seek re-election. Just as their Cup heroics in 1948 had helped them into the League then the 1971 FA Cup campaign ensured the U's earned a maximum 48 votes from their fellow clubs.
Smith brought wisely in the summer, bringing in Mike Walker and Mick Packer from Watford and splashing out a club record £11,000 on striker Paul Aimson.
Whilst Aimson suffered a career-ending injury early in the season, Svarc plundered 25 league goals including a record equalling four goal haul at Chester in November 1973.
U's led the table around Christmas time, but failure to beat Peterborough and Gillingham at Layer Road cost them the championship.
They also lost their first ventures into Sunday football losing at Bury and Doncaster by the same 2-0 scoreline.
Svarc's goals dried up at the wrong time, but the astute Smith brought in Gary Moore on loan and he scored 7 goals in 11 remaining games.
United were promoted in third place five points behind Peterborough and two adrift of the Gills. The final home game of the season drew a 10,007 crowd as Gillingham stole runners-up spot with a 2-0 win.
This would be the last time that Layer Road hosted a five-figure League attendance.
United were back in the Third Division but the board warned that a break-even gate of 9,200 was required and that players would be sold if gates didn't reach 7,500.
Smith returned to his old club Boston and signed Svarc's old strike partner John Froggatt.
The pair rekindled their partnership with Svarc netting 24 in the League with 16 coming from Froggatt. Crowds fell way short of the board's ambitions with an average of 4,941 clicking the Layer Road turnstiles as United finished in a steady eleventh position.
Having reached the Quarter Finals of the FA Cup only four seasons previously, United emulated that achievement in the League Cup.
Beating Oxford and Southend, the U's hosted First Division Carlisle beating the Cumbrians 2-0 to earn a home tie with Southampton.
A 0-0 draw at Layer Road led to an amazing 1-0 replay win at The Dell, courtesy of a Barry Dominey goal, setting up a Quarter Final tie with Aston Villa.
The Midlanders proved just a shade too strong for United winning 2-1 before an expectant 11,812 crowd. Whilst United's focus had been on the League Cup they were knocked out of the FA Cup by non-League minnows Leatherhead.
Out of the cups, fifth placed U's could concentrate on achieving Second Division football. Just one win in seven from New Year's Day onwards saw U's fall to mid-table and they never recovered.
The League Cup run had brought recognition - only it was for U's manager Smith who left to join Second Division Blackburn in the summer of 1975. His coach Bobby Roberts was appointed manager.
His early days were disastrous. Not only did United not win any of their first five games, but Smith returned with £25,000 to prise away Svarc from cash-strapped U's.
Roberts' side rallied mid-season to climb to twelfth place but some crushing defeats including 6-1 at Chesterfield and 6-0 at Brighton put Colchester back into the relegation mire.
The U's also suffered the ignominy of a second successive defeat to a non-League side when they were demolished 4-1 at Dover in an FA Cup replay. Inevitably United were relegated with Steve Leslie being leading scoring with a record lowest total of just six League goals.
The Board kept faith with Roberts for the 1976/7 campaign and, just as they did in the 1960s, United bounced back at the first attempt.
Built on 12 successive home victories from the start of the season United's 'G-men' Bobby Gough and Colin Garwood scored 17 and 16 goals respectively with centre-half Steve Dowman adding an amazing twelve strikes in his first season.
A splendid FA Cup run saw United reach the Fourth Round only to lose to First Division Derby in a replay at The Baseball Ground.Over 14,000 had seen Garwood equalise in the seventh minute of injury time in the first match at Layer Road.
Once again a settled side aided United's progress - eight players played over 40 of the 46 League games.
Colchester soared to the top of the Third Division table with four straight wins at the start of the following season.
Embarking on a League Cup run that saw United thump Jim Smith's Second Division Blackburn 4-0 in a Second Round replay before facing up to Leeds at Elland Road in the next round.
Leeds were not going to be embarrassed twice and gained some revenge with a 4-0 win.
When the U's visited leaders Wrexham on November 19th 1977, it was the first time that United had one of their League fixtures featured on the prestigious Saturday night TV slot.
One win in ten after January and the sale of Garwood to Portsmouth for £25,000 spelt the end of United's promotion aspirations.
Colchester finished in eighth place and eight points behind third-placed Preston.
Roberts kept faith with his squad but with a second injury to Eddie Rowles, Garwood's replacement, forced him into the transfer market.
Cash-strapped United splashed out £15,000 on Millwall's Trevor Lee who became the first black player to represent Colchester's first team.
Once again, United fell short of promotion finishing seventh - nine points behind third-placed Swansea.
In the final game of the season May 9th, 1979 United recorded their biggest ever away win in the League with a 5-1 romp at Tranmere less than a month after they had stunned champions-elect Watford with a 3-0 Good Friday win at Vicarage Road.
Colchester's season wouldn't be complete without the obligatory cup run and after disposing of Oxford, with a Gough hat trick, laying the ghost of Leatherhead with a 4-0 replay win at Layer Road and overcoming tricky away ties at Darlington and Newport, the U's welcomed Manchester United to Layer Road.
Called off from the original Saturday date, Colchester were so near to an Old Trafford replay only for Jimmy Greenhoff to break the hearts of most of the 13,171 crowd with a 86th minute winner.
The 1979/80 season had barely begun when United faced yet another top flight club.
Beating Watford over two legs in the League Cup, the U's were drawn at home to Aston Villa, rekindling memories of the Quarter Final tie five years previously.
A 2-0 defeat in front of just 6,221 meant to many that the tie was over, but remarkably United went to Villa Park and won 2-0 to take the game to extra time and then penalties.
So successful were all the takers that it was necessary for the goalkeepers to take their turn. U's stalwart Mike Walker missed his and Colchester bowed out 9-8.
The U's were in fine form in the League from then on going ten games undefeated and positioning themselves level on points with Sheffield United at the top.
Chairman Maurice Cadman announced that Layer Road needed £280,000 (over £1.5m in today's terms) of basic improvements just to meet the then safety legislation. Despite some grants being available the figure was unattainable.
The club could not relocate because a series of covenants was placed on the ground when it was purchased from the Council in 1971. One of those was that the club could not sell the land for housing.
Plans were drawn up to virtually lose the Open End by moving the pitch to create a 5,000 capacity terrace behind the Layer Road goal whilst building a new main stand on the Popular side of the ground with executive boxes. The capacity would increase to an 'adequate' 18,000.
Tracking the leaders for most of the season, with ten away wins to boot, United succumbed to successive defeats to Blackpool, Blackburn and Reading as February turned into March 1980 and, with injuries to Steve Foley and Bobby Gough, the goalscoring was left to Lee who returned 18 League and Cup strikes.
Colchester had occupied a top four slot for virtually all of the season but had to be content with fifth place and six points short of the promotion places.
It was the closest that the club had come to the dream of Second Division football since the 1956/7 season but the Colchester public had not responded.
The average gate of 3,818 was the third lowest in the division ahead of Wimbledon and Chester.Chairman Maurice Cadman's warning about the clubs financial difficulties was expected to spark an exodus of players. However, only Steve Dowman left in the summer joining Wrexham for £75,000.
The club received their first-ever shirt sponsorship from Royal London Insurance but failed to win in the opening eight games.
Beating Millwall 3-0 in the ninth attracted national coverage. Sergeant Frank Ruggles of Essex Police marched on the field and tried to arrest Lions' defender Mel Blyth for swearing.
Roberts signed unknown Highland Leaguer Kevin Bremner for a club record £25,000 and six consecutive home wins saw Colchester well placed at Christmas.
But when Trevor Lee moved to Gillingham in a club record deal worth £90,000 form dipped and United slipped down the table.
On transfer deadline day, Roberts matched the record fee in recruiting Roger Osborne and also paid £15,000 each for Roy McDonough and Phil Coleman.
Eight games without a win ensured relegation by just two points, and amid news of a 25,000 all-seater stadium development along the Avenue of Remembrance came the stark reality of a new all-time lowest attendance of 1,430 at the final day win over Carlisle and the season's average of just 2,641.
Roberts was given a vote of confidence despite relegation.
The Council refused the new stadium plans and re-iterated their covenant on Layer Road that prevented any activity other than football.
Three points for a win helped United hit top spot in Division Four by November 1981 scoring an incredible 41 goals. The U's also reached the FA Cup Third Round, drawing with Newcastle at St James's Park before losing a thrilling 4-3 replay.
Another £25,000 brought striker John Lyons who scored on his debut as Colchester thrashed rivals Sheffield United 5-2 in front of the Match of the Day cameras.
But a host of injuries and suspensions saw United free-fall down the table and Roberts was asked to resign in April 1982. He refused and was promptly sacked a month later.
Colchester had gone from promotion certainties to sixth, 16 points off the pace despite boasting a prolific strike force in Ian Allinson (26 goals), Bremner (24) and McDonough (16).
Former Ipswich centre-half Allan Hunter accepted a player-manager's role and introduced former Ipswich coach Cyril Lea as his assistant for 1982-83.
United led the table undefeated in seven games and earned a Second Round League Cup tie with Southampton.
The first leg was drawn 0-0 at Layer Road with England keeper Peter Shilton in inspired form. The U's could not repeat their heroics at The Dell of 1974 though, and lost the second leg 4-2.
The season then turned in the most tragic of circumstances.
John Lyons committed suicide at his Layer-de-la-Haye home in November 1982 just hours after turning out at Layer Road against Chester. On the back of having to give up his own playing career through injury and the Lyons incident, Hunter resigned in January 1982 with United in seventh place.
Lea took over until the end of the campaign and won 8 of his first eleven games. Four defeats in 17 days during April cost U's and again they finished sixth just two points away from promotion.
Allinson top scored with 24 League and Cup goals with youth product Tony Adcock netting 17 times. Goalkeeper Mike Walker, who had missed just nine games in ten seasons, announced his retirement.
Four months after becoming caretaker, Lea was appointed full-time with Stewart Houston assisting. He lost Allinson to Arsenal on an infuriating free transfer following an administrative blunder at Layer Road.
Always in touch with the leaders United embarked on another League Cup run.
Securing a fine 1-1 draw at Second Division Swansea United Chairman Cadman pledged that if more than 5,000 attended the second leg at Layer Road that he would give Lea funds to buy two more players.
The U's beat the Swans 1-0 in front of 5,204 and his promise was underwritten when Colchester drew Manchester United in the Third Round on November 8th 1983.
The 13,031 crowd would be the last-ever five figure gate at Layer Road and the slick Red Devils ran out comfortable 2-0 winners.
As had become the norm U's form tailed off and they ended 15 points adrift of promotion in eighth place despite Adcock's 31 goals.
Frustrated by his Board's attempt to fund promotion that continually ended in close failure, Chairman Cadman announced that win bonuses would be dropped for the 1984/5 season with an insurance-backed promotion bonus on offer and the club was available for sale at £150,000.
Attendances continued to fall and a new low of 1,226 watched the 3-0 win over Torquay on April 28th 1984. Micky Cook, who had set a club record 613 appearances, and Steve Leslie both retired through injury.
Only three of the eight players out of contract chose to move on despite the new bonus scheme. The biggest loss was Steve Wignall who joined Brentford.
Remarkably United were paired with Gillingham in both major Cup competitions and the Freight Rover Trophy.The 5-0 FA Cup thrashing at Layer Road on December 8th 1984 became United's biggest ever home defeat.
Adcock continued to score at will and by January had 28 goals to his credit.
It was rumoured that Liverpool were only a signature away from his capture, but a cruel knee injury virtually finished his season in which he surely would have smashed Bobby Hunt's 38 goal club record.
United also lost their shirt sponsors but Cadman finally got his buyer when Jonathan Crisp paid £150,000 for overall control of United.
He promised Second Division football within five years but in the light of the horrific Bradford fire the timber-constructed Layer Road stands and terracing meant that it was of utmost importance to accelerate United's move to a new stadium.
As was becoming the norm, United were just not quite good enough for promotion finishing seventh and ten points adrift of fourth place. The club equalled its record away win with a 5-1 return from the March 23rd 1985 trip to Exeter but worryingly average crowds totalled just 2,076.
With Heysel following on the heels of Bradford, Layer Road faced £500,000 worth of safety improvements. With no money, the club closed areas of Layer Road reducing capacity to 4,900.
Lea continued the policy of recruiting ex-Ipswich players. Topping the table in October 1985, the U's imploded, suffering six successive League defeats, four without scoring, and were knocked out of the FA Cup by non-League Wycombe.
Lea could not find a strike partner for Adcock following Keith Bowen's career-ending car crash.
The manager had a good record and produced a free-scoring side but could not get the club over the promotion finishing line and three weeks from the end of the season he was sacked.
Former goalkeeper Mike Walker, coach of U's reserves, took over as Caretaker and United were unbeaten in the remaining eight matches - winning five. Walker had hoisted U's to seventh just nine points short of promotion.
It was a notable season for hat tricks with Perry Groves twice achieving the feat against Southend and brothers Tommy and Tony English scoring trebles within five days of each other.
The English brothers were both sent off at Crewe in a game which United won 2-0.
Colchester were the bookies favourites for 1986/7 despite selling Groves to Arsenal for £75,000. Maurice Cadman handed over the Chair to Crisp and Walker was appointed full-time becoming Colchester's fourth manager of the 1980s.
For the first time promotion play-offs were introduced and seven successive away defeats from December ensured The U's would have to try via this route having finished fifth.
The damage was done in a rain-sodden first leg at Layer Road as a near capacity 4,829 saw Wolves escape with a 2-0 win. The scoreless return at Molineux meant yet another season in the basement division.
Adcock decided it was time to move on and £80,000 saw him join Second Division Manchester City. Walker recruited former U's boss Allan Hunter as his coach whilst Crisp announced an ill-advised bombshell.
In light of the worsening hooliganism countrywide he adopted a 100% members-only scheme banning away fans.
To deflect the furore Crisp leaked details of a proposed new stadium at Turner Rise and introduced developers Norcross Estates as shirt sponsors.
Only 1,300 members attended the first fixture of the 1987/8 season, a drop of 1,400 on the previous average.
Walker broke the club's transfer record spending £40,000 on striker Dale Tempest while a new lowest crowd was set as 1,140 watched the September 29th 1987 win over Swansea.
Having rebuilt his side winning seven out of eight games Walker was sensationally sacked by Crisp as United were joint top of the Fourth Division.
Crisp claimed Walker had resigned, but an alleged personal matter between the pair was said to have been the spark. Walker was awarded Manager of the Month after he had been sacked.
New manager Roger Brown took over a successful team and destroyed it. Recommended to Crisp by his 'advisors', Brown had been a factory manager and in charge at Poole Town.
From top spot on New Years Day Brown's team won just five games to finish ninth - United's lowest position for 15 seasons.
When hundreds of Wolves fans claimed membership and 'boosted' the Layer Road attendance to 2,413, Crisp scrapped his membership scheme declaring it had only been an experiment.
The seeds of United's sad demise had been sown and the season's average was a paltry 1,769.
Crisp considered selling Layer Road and ground sharing with Ipswich whilst the Turner Rise stadium was built.
Fortunately he was swayed by a group of ex-directors of the club. Crisp would have recouped his outlay, but when the stadium plans were delayed, over land ownership, United would have been totally homeless with no assets bar players.
Brown brought in more of his own 'talent' and United nosedived. Having already inflicted United's joint record defeat of 7-0 back in 1952, Leyton Orient went one better and despatched Brown's sorry team by 8-0 at Brisbane Road on October 15th 1988.
The manager's days were over. Caretaker Steve Foley disposed of Brown's misfits introducing his own youth team players Gary Bennett, Mark Radford and Scott Daniels.
Whilst League form did not improve - United sunk to 92nd, a position they had not occupied since 1972 - Foley's team embarked on a typically Colchester FA Cup run. Defying the odds they saw off Fulham, Swansea and Second Division Shrewsbury.
In the Fourth Round, a dramatic 3-3 draw at Bramall Lane forced Sheffield United back to fog-shrouded Layer Road. U's lost 2-0 but they had the mercurial former Glasgow Rangers manager Jock Wallace in charge with England World Cup winner Alan Ball as his assistant.
The impact was immediate.
Crowds rose to over 3,500 as the town became gripped by the passion of Wallace and an equal desire to avoid the drop to the GM Vauxhall Conference.
Paul McGee was sold to Wimbledon for a new record £150,000 fee and on April 29 1989 United travelled to closest rivals Darlington in a do-or-die battle.
Robert Scott's goal earned a 2-1 win to lift U's off the bottom for the first time since Brown's departure.
Two successive home wins against Halifax and Exeter confirmed U's Fourth Division status.
Hopes of building on the Wallace regime were tattered when Colchester failed to win any of the opening eight games of 1989/90.
Only two wins were secured before the turn of the year. Ball left for Stoke and it was a closely guarded secret that Wallace was very ill with the onset of Parkinson's Disease.
Wallace moved upstairs and once again Foley was in temporary charge. Many wanted him appointed permanently but Foley preferred his youth team duties.
Crisp's regime was now over £1m in debt and his next new manager was former Ipswich and England defender Mick Mills, recently sacked from Stoke.
The new appointment had immediate effect as U's won three out of four in February and, as with the season before, faced up to a crunch game at the home of their nearest rivals. Leading Wrexham twice United succumbed to a 3-2 defeat.
There was still time to recover but six defeats in the last eight games ended United's 40 season Football League tenure.
Crisp's dream of Second Division football in five years was light years away and new plans for a stadium at Wick Lane, Ardleigh had been thrown out before ink was dry.
Colchester bowed out of the Football League with the following record:
Fourth Division runners-up: 1961/2
Also promoted: 1965/6, 1973/4, 1976/7
Best finish: 3rd in the Third Division South 1956/7
Relegated: 1960/1, 1964/5, 1967/8, 1975/6, 1980/1, 1989/90
Re-elected: 1953/4, 1954/5, 1972/3
FA Cup: Quarter Finalists 1970/1
League Cup: Quarter Finalists 1974/5
Watney Cup: winners 1971/2