Imagine Carlisle United’s blue-clad heroes walking out at Wembley to compete in the FA Cup final. Just imagine the big groove in the Cumbrians’ history had it ever happened.

Well, the closest they came also happened to be their most high-flying campaign of all: the 1974/5 season, when United were competing in the First Division.

Their efforts in that sweet, solitary season at the summit were accompanied by what remains their best attempt of all in the country’s most famous knockout competition.

They got as far as the last eight, before one of those agonising defeats, in the quarter-finals, that left fans wondering for some time afterwards quite how it had happened.

United’s visitors that March day were Fulham from the Second Division. Carlisle had secured the home tie by defeating Preston North End in the third round and West Bromwich Albion the fourth, before Bobby Owen’s goal at Mansfield Town in round five sent Alan Ashman’s side further.

News and Star: United edged past Mansfield in the fifth round, pictured, to set up their quarter-final tie with FulhamUnited edged past Mansfield in the fifth round, pictured, to set up their quarter-final tie with Fulham

The Blues were, at the time, locked in a struggle to prolong their top-flight adventure but had grounds to think that, whatever happened in the league, it could still be a season to savour in the FA Cup.

Fulham were embarking on a mid-table journey in the division down but the team sheet they submitted at Brunton Park still caught the eye. In defence was a certain R.Moore – England’s World Cup winning captain Bobby, no less – while Alan Mullery was another international star entering his veteran years.

In goal, meanwhile, was the blond-haired former Burnley man Peter Mellor, who deferred to his opposite number Allan Ross in the experience stakes – but who would go on to leave a lasting and unwanted mark on United’s FA Cup history.

A crowd of 21,570 showed up hoping to see Ashman’s side overcome their lower-ranked visitors and reach the last four. The manager had scouted the Cottagers in midweek against Millwall and reckoned Alec Stock’s men were a “good, well-organised side” for whom Mullery was a typical creative influence.

News and Star: United's Bill Green wins an aerial tussle against FulhamUnited's Bill Green wins an aerial tussle against Fulham

Six trains brought fans of the London club north – and Carlisle set about trying to derail their guests. Owen volleyed over the bar early on when a Moore clearance fell his way, before the legendary Fulham defender sliced a shot wide at the other end.

United had a better chance after ten minutes when Moore obstructed Joe Laidlaw in the box and the Cumbrians gained an indirect free-kick. This proved to be Mellor’s first intervention of many, as the keeper superbly kept out Laidlaw’s shot at the far post.

Carlisle remained on top but found the opening goal elusive. Mellor made further saves while Bill Green missed with a diving header. United did have a scare when Viv Busby evaded Ross, but the retreating John Gorman saved the Blues in the goalmouth.

Mellor once more kept out an Owen shot after the forward had been fed by Chris Balderstone, and all this was packed into a lively opening 20 minutes.

News and Star: Fulham keeper Peter Mellor, second right, clears the visitors' linesFulham keeper Peter Mellor, second right, clears the visitors' lines

The tempo eased somewhat from there, with defences on top – Moore coming into his imperious own – while a congested midfield battle offered few clues as to who might come out on top.

Ray Train missed a decent opportunity for the Blues, while for Fulham, Jimmy Conway – whose three-year-old son Paul would grow up to play for Carlisle – threatened after a raking Moore ball, only to be denied by Peter Carr.

Laidlaw went close before the break, after which the same man went through only to be penalised by ref Gordon Hill. Mellor was further defiant for the visitors – and then United’s frustrations were ramped up when Fulham took the lead in the 67th minute.

It was one of those slow-motion goals which, to this day, remains a difficult watch, Busby buzzing down the Fulham right, Carr and Ross getting into a muddle over who should deal with his low cross, and Les Barrett sweeping home the loose ball at the Waterworks End.

It was a cruel, crushing blow and teed up an upset for the visitors. After Conway had been stretchered off after a challenge with Carr, Carlisle sought to get back into things – but once more met the inspired figure of Mellor.

News and Star: United on the attack against Fulham at a packed Brunton ParkUnited on the attack against Fulham at a packed Brunton Park

He superbly tipped over a Les O’Neill volley, while a later scramble involving O’Neill, Green and Owen failed to deliver the equaliser. Stock’s side held on – and United, via a 1-0 defeat, were out of the cup.

It proved quite the anti-climax and let to plenty of soul-searching among the Blues. Ross, the legendary goalkeeper, fronted up in his newspaper column and wrote that Fulham’s goal was “by far my worst moment in 12 years with United…I can do no more than hold my hand up and strive for peace of mind.”

The great keeper had more than enough credit in the bank from his sterling United service, which made him the club’s record appearance maker. Manager Ashman also pointed out that it was a collective defeat, and that he would not have talk of scapegoats.

It was, though, a “crucifying” loss, he also admitted, and, without the happy distraction of a cup run - Fulham went on to lose to West Ham in the Wembley final - United were left to try and salvage their top-flight status. Alas, that proved beyond them, and they went back down to the second tier, after a season when they had flown closer to the sun than any other point in their long and eventful history.

United: Ross, Carr, Gorman, O’Neill, Green, Parker, Martin, Train, Owen, Laidlaw, Balderstone. Sub: Spearritt.

Fulham: Mellor, Fraser, Strong, Mullery, Lacy, Moore, Dowie, Conway, Busby, Slough, Barrett. Sub: Lloyd.

Crowd: 21,570.