His father Aidan’s name went into the record books as trainer of the 2016 winner, but O’Brien junior was given credit for the preparation – and now has a major fancy in his own right in the four-year-old championship at Cheltenham on Friday.
O’Brien, who scored his maiden Festival victory with Band Of Outlaws on Wednesday, inherited Sir Erec from his father after the Camelot colt’s decent Flat career – which included finishing third to Stradivarius in the Qipco British Champions Long Distance Cup at Ascot in October.
How good was Sir Erec's win at Leopardstown last time?
He has transferred his smart form to jumps, with highly-promising wins in both his starts.
After beating 27 rivals on his debut in a maiden hurdle at Leopardstown over Christmas, Sir Erec returned to the Dublin track to lift the Grade One Spring Juvenile Hurdle by an easy six lengths in February.
A slight injury scare last week failed to dampen enthusiasm for the short-priced ante-post favourite.
“Obviously he has taken to hurdling well,” said O’Brien. “He ran a nice race first time and improved a good bit to his second run. He’ll have to improve again, but we’re hopeful he’s capable of doing so.
“Maybe the (Triumph) field might not be as big as it used to be, but all the good ones will still be there. It’s going to be a competitive race – and by far his biggest test so far – and he’ll probably have to run a career-best to win it.
“We’re very realistic in that sense, but we’d like to think he has a favourite’s chance.
“He was visually very impressive the last day, and I’ve never hidden the regard we hold him in. He’s very exciting.
Watch how Sir Erec finished third to Stradivarius on the Flat
“He’s won his last two races on good ground and won a Listed race on heavy ground on the Flat, so he seems pretty ground-versatile.”
Tiger Tap Tap was only a neck behind Sir Erec in that Leopardstown maiden hurdle, and he carries plenty of confidence from the Willie Mullins stable.
“I think Tiger Tap Tap has a huge chance. His form with Sir Erec at Christmas is his true form,” said Mullins’ son and assistant Patrick.
“Sir Erec dominated from the front in a slowly-run race on fast ground the last day, which suited him as an ex-Flat horse.
“We hope in a fast-run race Tiger Tap Tap will be able to get close to him again.”
Mullins feels the yard’s other two runners, Runrized and French Made, have plenty to find on form. “The other two need to step up,” he said.
John McConnell is hoping conditions dry out to allow him to run Hannon.
“We’re still 50-50 about running. We’re hoping it’s going to dry some,” said the County Meath handler.
“He’s never gone on ground as soft as it is there now. If good to soft comes back into it by Friday, which is a possibility, then we will probably have a go.
“It’s competitive, and the favourite will be hard to beat, but we hope we have an each-way chance. He’s in great form. We’d like to run, but we’re not going to empty him on soft ground.”
Quel Destin has continued to thrive since his Cheltenham win
Leading the British bid is the Paul Nicholls-trained Quel Destin, who has been a revelation in his juvenile campaign.
The French-bred gelding has won the last five of his six starts in Britain, including the Grade One Coral Finale Juvenile Hurdle.
“He just got beat first time out at Chepstow for us,” said Nicholls.
“He was a bit green that day and inexperienced in regards to hurdling and British racing. He won a Grade One at Chepstow over Christmas. He has won a couple of Grade Twos, one at Cheltenham.
“He came back at Haydock the other day and won the Victor Ludorum. I was surprised how well he won, because he was big and well and I thought he need the run.
“He is a proper tough four-year-old – what you want in the Triumph. He can make the running if they go no gallop. He can be nice and handy.”