The midfielder broke the deadlock with a blistering long-range strike 20 minutes into the second half and, though Federico Macheda won and converted a penalty to earn extra time for a much-changed United side, Glenn Murray headed the winner from Ambrose's free-kick.

"It's fantastic," Ambrose told Sky Sports 1. "It was a great occasion coming here against the champions.

"It was a massive occasion for the fans."

Cardiff await in the last four after the draw was made following tonight's match, meaning one npower Championship club will take on either Manchester City or Liverpool at Wembley.

Tonight's win was made all the more remarkable by a poor run of Championship form, which has seen Palace go five games without a win or a goal.

"We've had a quiet period in the season but we came here in confident mood and the spirit is fantastic," Ambrose continued.

"We've got a great team spirit, it's a lot different from last year - we can beat anyone, and we showed that tonight.

"We weren't worried about the lack of goals, we've got goalscorers and that showed tonight, it was a great finish from Glenn on the second."

Manager Dougie Freedman, who has earned plaudits for his work since taking over a cash-strapped club midway through last season, added: "It's a wonderful night for the club, especially given the position we've been in the last few years.

"To play at Old Trafford tonight, we're privileged, the lads learnt a lot from tonight.

"I think we deserved it. We played some stuff, some good football.

"We thought if we came with a gameplan that could be stuck to and everybody played eight, nine, 10 out of 10 we could do it."