Superstar two-miler Altior makes his debut at three-miles this weekend as he looks at a possible Gold Cup challenge.

Altior, unbeaten in 19 races is the undisputed number one over two miles, but now trainer Nicky Henderson has switched him to three miles as he bids to become one of racing’s all-time greats.

Altior will begin his three-mile career this weekend at Ascot and will come up against one of the leading lights in Cyrname.

Henderson said: “Why step up in trip? It’s media pressure, thanks guys. Everybody says it is boring watching him go round over two miles, so let’s show us what he can do.

“If you saw him last Friday, you would have thought this can’t be the right thing. It’s just crazy, he has got so many gears and you can’t believe he is a genuine stayer. If he is a stayer, he is the most remarkable horse I’ve ever seen.

“The timing of this race is right. It’s lovely you have two horses like this and people are building it up to be something quite exciting, that might be worth going to watch. It’s the sort of clash you do want.

“I think it is exciting. It is good stuff and you would rather be involved than not. We will be the ones slightly a bit more jumpy than everyone else. We are putting on the show.

“If he is a true champion he has got to be able to do it over a variety of distances and this is where we are testing it. There are a lot of questions to be answered and a lot to prove.”

William Hill can report further money for Altior and the book is now 71% in favour of Nicky Henderson’s star, compared to 29% for Cyrname.

“There are a lot of people who have made money backing Altior and they are clearly coming in again,” said William Hill spokesman Rupert Adams.