Jockey Jamie Spencer gave David Junior a great ride

The Brian Meehan-trained colt held off French raider Pride, a 12-1 chance, by three-quarters of a length.

Sir Michael Stoute's Maraahel, another 25-1 outsider, finished a further one and a quarter lengths away in third.

Meanwhile, Sergeant Cecil completed an unprecedented hat-trick with victory in the Totesport Cesarewitch Handicap after previously landing the Northumberland Plate and Ebor.

Spencer, who is set to become champion jockey for the first time, was not unduly surprised by his Champion Stakes win on David Junior.

"It was a tough race and the bookies gave us no chance, but I rode him at Goodwood and I really liked him," said Spencer.

"He travelled so well in the race.

"I think I gave him a bad ride as I went way too soon on him - he is a long-striding horse and he got into a rhythm so I just let him go and he really picked up.

"Brian said it is a Group One but to ride it like a normal race - get him nice and relaxed and ride the race as it comes to you."

Earlier, Sir Percy emerged as a genuine contender for next year's 2,000 Guineas when claiming the Darley Dewhurst Stakes.

Sir Percy, sent off at 9-2, hit the front inside the final furlong and kept on well to hold 8-11 favourite Horatio Nelson by a neck.

He just came off the bridle a bit at halfway but once he kicked on he really flew Marcus Tregoning Trainer of Sir Percy

Opera Cape finished a length and half back in third.

"He's a really good horse, the real deal. I've always had a lot of faith in him," said winning jockey Martin Dwyer.

"He has not run for a while and he's a bit fresh and full of himself, but I was really impressed with him. He just idled a bit when he heard the crowd."

Trainer Marcus Tregoning added: "He's been working very well at home and Martin has been telling me all week how confident he was.

"He just came off the bridle a bit at halfway but once he kicked on he really flew. I still think he's a bit green but he's learning with every race."

It's a great piece of history and I'm just pleased to be part of it Alan Munro on Sergeant Cecil

Sergeant Cecil, sealing a unqique staying handicap treble, burst through in the closing stages under Alan Munro to win going away from King Revo at odds of 6-1.

Three-quarters of a length separated the pair at the line, with Inchnadamph a further two lengths away in third.

"It's wonderful to achieve the treble," said trainer Rod Milllman.

"But you can't do it without a good horse, great staff and a good jockey."

Darley Dewhurst Stakes 7f
1 Sir Percy M Dwyer 9-2
2 Horatio Nelson K Fallon 8-11f
3 Maraahel R Hills 25-1
15 ran. Dist: nk, 1�
(M Tregoning)

Emirates Airline Champion Stakes 1m 2f
1 David Junior J P Spencer 25-1
2 Pride C Soumillon 12-1
3 Maraahel R Hills 25-1
15 ran. Dist: �, 1�.
(B Meehan)