"You can't make a mistake like that against horses of the calibre of Imperial Commander, Denman and Cooldine.
"You are always struggling and I was fighting a lost cause. It was a bad fall but he got up and there's not a bother on him. He cantered back down fresh as a daisy, not a bother on him."
Denman's part-owner Harry Findlay was delighted with his charge's display but also paid tribute to the winner's achievements.
"It was a great performance. I thought in running we were going to win it, but Imperial Commander has shown a lot of class and speed and all I can do is take my hat off to him," he said.
"Denman looks a National horse through and through and I'd be very surprised if he doesn't take in next year's race."
Imperial Commander's win proved to be the first leg of a 747-1 treble for Twiston-Davies.
Baby Run (9-2jf) landed the Christie's Foxhunter Chase, leading from start to finish under the trainer's son Sam before Brennan guided Pigeon Island (16-1) to success in the Johnny Henderson Grand Annual Chase.
Despite the Gold Cup win, Twiston-Davies admitted that the Foxhunter victory gave him most pleasure.
"I was hugely proud of Sam and he rode a beautiful race. The horse was a write-off when I got him, but we managed to get him back.
"That has to take the biscuit. It was a long run to the line, but he was lonely for company and came home with his ears pricked. He didn't look that tired.
"He'll go to the Aintree Foxhunters' next and he'll remain hunter chasing next season."
Despite his disappointment on Kauto Star and also on Master Minded earlier in the week, Ruby Walsh ended up as the leading jockey at the meeting for the fifth time.
His wins on Big Buck's in the Ladbrokes World Hurdle, Quevega in the David Nicholson and Sanctuaire in the Fred Winter meant he was level on winners with Barry Geraghty but a couple more second places saw him collect the trophy.
Three winners for Nicky Henderson - including the day's opening race with Soldatino (6-1) in the Triumph Hurdle - allowed him to win the Thomas Pink Leading Trainer award for the first time since 2000.
Two big outsiders were also returned at a meeting which was probably the best ever for bookmakers, Thousand Stars (20-1) - with Katie Walsh on board - and Berties Dream (33-1).
The Emma Lavelle-trained Pause And Clause (14-1) picked up the Martin Pipe Conditional Jockeys' Handicap Hurdle with Johnny Farrelly on board.
Cheltenham Gold Cup
1. Imperial Commander (P J Brennan) 7-1
2. Denman (A P McCoy) 4-1
3. Mon Mome (A Coleman) 50-1
11 ran