Saints striker Bobby Stokes shocked the football world with an 83rd-minute strike that beat full-stretched United keeper Alex Stepney.

Time stopped in the city of Southampton and its satellite towns and villages. The Hampshire air erupted with car horns and cheers from tens of thousands of living rooms that for the best part of that David v Goliath afternoon had been silent and breathless. TV screens around the world beamed pictures of those lucky enough to get a ticket dancing in delirium on the terraces of that famous twin-towered old stadium – one half of the 99,115 crowd on a natural, legal high only football can offer.

This schoolboy memory continues to make neck hairs stand to attention.

Back then domestic cups meant something. The FA Cup was viewed by many as a bigger prize than the First Division title, and the League Cup was deemed the next best piece of silverware.

Players respected the competition. They wanted a meaningful medal from their careers and the League Cup offered one of the few available. Fans were desperate to win it, as were managers and prestige-hungry club owners. All effort was put into claiming the trophy – more so if you were knocked out early in the FA Cup.

The fielding of second-string outfits of youngsters put out to make up the numbers was unheard of. Such an insult would not have stood: win the League Cup and you earned respect from jealous rivals, to claim this crown meant the football world took notice of your team, if only for a week.

Since the start of the century and the exponential rise and global appeal of the Premier League with all its riches and glamour, plus the growing influence of the Champions League, managers in the top six English clubs have sniffed at the competition. Even middle-table pedestrian teams and relegation strugglers view it as a hindrance.

In 2010, Arsenal manager Arsene Wenger said a League Cup win would not end his team’s trophy drought. Manchester United’s then manager Alex Ferguson retorted that the cup “was a pot worth winning”, which his team duly did that year, beating Aston Villa 2-1 to become the first team since 1990 to retain the trophy, having beaten Tottenham in 2009.

Some suggest the fielding of weakened top clubs offers lesser teams the opportunity to partake in some giant killing. But slaying a lame, half-baked behemoth is not the same as scalping the real thing; the fairy tale loses its romance. And such arrogance smacks of a football apartheid based solely on the size of a team’s bank account.

Besides, Mourinho has much to prove and views the League Cup in the same vein as Ferguson; any cup is better than none.

Having cruised through to the next round of the Europa competition midweek, still gunning for a top-four league finish and still in the FA Cup, Mourinho will be keen to show he is turning lumbering Old Trafford back into a successful silverware collector.

Trophies guarantee little, of course, as Louis van Gaal can attest after leading United to last year’s FA Cup against Crystal Place only to walk the plank, a title arguably less so after events at Leicester.

United supporters will dominate Wembley, a turf they consider their second home. For such regular visitors and serial winners – they have their names engraved four times on the League Cup – another victory, of course, would be welcomed but far from extra-special.

It’s a different story for Southampton supporters. A win would be the south coast club’s first major trophy for nearly two generations – and victory against old foes United all the sweeter, a cherry to top a barnstorming week.