City hit united for 6'.

Ferguson, who celebrates his 25th anniversary as United manager on Nov 6, witnessed his club’s biggest derby defeat since another 6-1 loss to City in January 1926 — just one short of United’s record home defeat, a 7-1 loss to Newcastle in September 1927.

Playing with 10 men following the 47th-minute dismissal of defender Jonny Evans, United on Sunday capitulated in the dying stages as City ran in three late goals. But with City moving five points clear of United with their emphatic victory, Ferguson admitted he had never experienced such a dark day as a manager.

“It was our worst ever day,” Ferguson said. “It’s the worst result in my history, ever. Even as a player I don’t think I ever lost 6-1. I can’t believe the scoreline. The first goal was a blow for sure, but it was retrievable at 1-0.

“I’m shattered, I can’t believe it. It was an incredible disappointment, but we will react, no question about that. It’s a perfect result for us to react to because there is a lot of embarrassment in the dressing room — and quite rightly so — and that will make an impact. You have to recover. The history of Manchester United is ‘another day’ and we will recover.”

The humiliation of United’s defeat resulted in the club’s American owners, the Glazer family, being barracked and jostled by home supporters as they travelled from the players’ tunnel to an awaiting helicopter.