Expensive colt Hydrogen is finally scheduled to make his racecourse debut at Newmarket on Friday.

The Galileo colt was the most expensive yearling sold at auction in 2012 when snapped up by Qatar Racing for 2.5 million guineas ($A3.985 million).

Peter Chapple-Hyam, who also trained his Derby-winning half-brother Authorized, has endured a torrid run with Hydrogen who suffered a leg injury in April last year.

He recovered but his debut was again delayed when he returned an unsatisfactory scope late last year.

He has not been hurried into action this term, but is due to make his long-awaited debut in a 12-furlong (2400m) maiden.

He is one of 11 declared runners along with recent Ascot third Wonderstruck, a half-sister to Grandera and George Washington, Hatsaway and Obstinate.