Believing and Mill Stream have been supplemented to take on Shaquille in the Betfair Sprint Cup at Haydock on Saturday.

A total of 23 speedsters are in contention for the six-furlong Group One, with the Julie Camacho-trained Shaquille very much the star attraction as he looks to add to his previous top-level wins this summer in the Commonwealth Cup at Royal Ascot and the July Cup at Newmarket.

The George Boughey-trained Believing and Jane Chapple-Hyam’s Mill Stream are two interesting contenders after their respective connections paid the £20,000 required to add them to the field.

Believing has won two Listed races and a Group Three this season and is one of two potential runners for the Highclere Thoroughbred Racing team along with Karl Burke’s Spycatcher, who was beaten a short head by King Gold in the Prix Maurice de Gheest at Deauville last month.

However, the latter appears unlikely to make the trip to Merseyside.

Harry Herbert, Highclere’s managing director, said: “Believing was impressive winning last time and the way she has been since leads George to think she’s improving rapidly.

“Certainly looking at her physically that is exactly what she’s doing, so we looked at all the options for her and felt this was an opportunity to have a crack at a Group One race.

“With ground conditions quickening up it’s possible the field will reduce, but it’s more the way she’s coming into the race and the opinion the trainer has of her.

“She’s very smart and with a filly like this that’s improving, the shareholders were keen to give it a go and it’s very exciting.”

Of Spycatcher, Herbert added: “He’s in great form the horse, but we definitely wouldn’t risk him on quick ground.

“This has been the target for a while now, but it’s highly unlikely that he’ll run looking at the forecast. You never know, if a thunderstorm hits or something happens before declaration time then we may reconsider, but we need to protect him.

“He’s in at Ascot on Champions Day and we’ve got to be patient. He’s a wonderful horse who is improving all the time, but at this stage I’d say we’d struggle to run him on Saturday unless something out of the ordinary happened with regards to the weather forecast.”

Mill Stream won a Listed race and a Group Three at the French track in August and fully merits his place in Group One company.

“Mill Stream has come out of his Deauville race in good order, so we have decided to take the opportunity to run him again while he is good form as there are no other options for him until Champions Day,” said Chapple-Hyam.

Ralph Beckett has left in both Kinross and Lezoo after on Sunday suggesting he is likely to rely upon the latter, while Aidan O’Brien could saddle one or both of Aesop’s Fables and The Antarctic.

Other hopefuls include Ed Bethell’s Regional, the William Haggas-trained Sacred and July Cup runner-up Run To Freedom from Henry Candy’s yard.