Matthew Chadwick has secured the ride on the enigmatic Silver Express for next weekend’s BMW Hong Kong Derby (2,000m) and is excited by the unknown that comes with partnering the John Size-trained galloper.

The four-year-old steps up to 2,000m after never running further than 1,400m in his seven career starts but Chadwick was more than happy to put his faith in the master trainer, who prepared Ping Hai Star to win the 2018 Derby after making the same jump in distance.

“It’s always good to get on one of John Size’s horses and it’s exciting to get on a horse like that,” the jockey said.

“We don’t know exactly what’s going to happen with him but he looks like he’s taking the right steps and the race is going to be wide open.”

No superstars, but the Hong Kong Derby should be a cracking race

After throwing away victory at his second Hong Kong start by veering sharply to his left in the dying stages, Silver Express returned with a dominant victory under Joao Moreira late last month to rocket into Derby calculations.

Chadwick rode the horse for the first time in a trial at Sha Tin on Tuesday morning, with Silver Express hitting the line nicely for second behind fellow Derby runner Russian Emperor.

“He’s very interesting. He obviously hasn’t been over further than 1,400m but his win last time was quite impressive, albeit at top of Class Three against average opponents,” Chadwick said.

Chadwick switches to Silver Express after partnering Packing Waltham to sixth in the Classic Cup, leaving Neil Callan to pick up the ride on the Tony Cruz’s progressive French import.

“I was taking a wait-and-see approach because it was so wide open. Packing Waltham ran a good race but he’s still in the process of acclimatising to Hong Kong so I didn’t push for the ride but then I got told they wanted to replace me anyway,” Chadwick said.

“After Silver Express won I heard a rumour that he might be running in the Derby so I sent John a message. He said ‘stay tuned, we have to see how the horse pulls up’ so I waited and he called me back with the news.”

Size was pleased with the trial of Silver Express and while he confirmed his charge will tackle the Derby, he stopped short of predicting whether he will handle the trip.

“We’ll find out race day, it’s hard to tell but he seemed to trial quite well and he’s an honest, determined racehorse,” said Size, who was also pleased with how his other Derby entrants Excellent Proposal and Lucky Express performed in the same hit-out on Tuesday morning.

Size remarkably takes only last-start winner Wind N Grass to Happy Valley on Wednesday night while Chadwick has eight rides including the mount on Casimiro, who chases his fourth win of the season in the Class Three Bulkeley Handicap (1,800m).

“He’s been racing very honestly, he’s drawn quite awkwardly [in gate eight] and the B course is going to be a bit of a task – we’re going to have to sit down and work out the right path,” Chadwick said.

“His last run was good again from an awkward gate so we know he puts his best foot forward and he tries his best.”