Rajasinghe came out on top after a thrilling climax to the Coventry Stakes at Royal Ascot.
The Richard Spencer-trained colt was an 11-1 chance after making an impressive debut at Newcastle last month and was produced to challenge down the centre of the track by Stevie Donohoe.
Headway, carrying the colours of the Royal Ascot Racing Club, finished strongly nearer to the stands rail and they flashed by the post almost as one, but the judged confirmed Rajasinghe the winner by a head.
Murillo was third, with Jessica Harrington's 4-1 favourite Brother Bear only fourth after hanging badly in the final furlong.
Donohoe said: "Being drawn nine I thought was a nice draw, but it ended up being a bad draw because I had nothing to aim at.
"He stays well and he came good about a furlong and a half out. He's done all his work on his own so I think it's more impressive that it looked.
"He's a big boy, full of life and we love him to bits, I think he'll be better at three as well."
He added: "I dislocated my fingers last night and all night they were giving me trouble. I took the straps off down at the start hoping the adrenaline would get me through.
"We'd been really happy with his home work, the only worry we had was running on turf.
"It's great for the underdog, to take on the big boys and win is great."
Phil Cunningham had the pleasure of owning dual 2000 Guineas winner Cockney Rebel and now runs Rebel Racing.
He said: "It was always the dream to win here after winning the Guineas. This is the first horse I've bought off Bobby O'Ryan since Cockney Rebel, 10 years ago. He's named after one of the owners, Raj, a good friend of mine.
"He was a little slowly away but he's a super horse, we've liked him for a long time but however well you think they are doing, to come here and do it is a dream."
Spencer said: "He's an amazing horse and I've loved him since day one.
"He's done everything I've asked and leading up to Newcastle he was definitely not over-screwed going into that. I knew there'd be improvement and he's taken that step forward today.
"The staff have been amazing with him at home, as has Phil Cunningham and everyone who has given me the opportunity to train him - it's an absolute dream and just amazing.
"He's going to stay seven furlongs. He's a proper horse."
Harry Herbert, racing manager for the Royal Ascot Racing Club, said of Headway: "He's run a fantastic race and you just can't crab him as he's such an honest horse.
"We thought he'd run well and the signals William (Haggas) was giving out was that he was pleasing him at home.
"He was impressive at Chester and to be beaten a head in a race like this is agony, but it's great for the Royal Ascot Racing Club that they got to have a shout here and they've got a very good two-year-old.
"I guess we'd be keen to take on the winner again, but he's had a hard race today. I think we'll stick at six for the time being."