Dwyer has won both the Oaks and Derby at EpsomThe 2006 winning jockey Martin Dwyer will replace banned rider Jamie Spencer on Regime in the Epsom Derby on 2 June.
Dwyer, who triumphed on Sir Percy last year, was booked by trainer Michael Bell after Spencer's suspension.
Former champion Spencer will miss the Derby meeting after losing his appeal on Monday to overturn a suspension imposed by French stewards.
Spencer got two bans - one for six days and one for four - for his riding in the French 2000 Guineas on 13 May.
The 26-year-old was contesting the four-day suspension but France Galop rejected his appeal.
Spencer was due to ride second favourite Dalvina in the Oaks on 1 June and 20-1 chance Regime in the Derby.
French jockey Oliver Peslier is now likely to be on board Dalvina.
In other jockey news, Ted Durcan has been secured by trainer David Elsworth to ride his Derby contender Salford Mill, currently second favourite behind Authorized.
Dwyer boasts good form around Epsom, having tasted Classic success on board Casual Look in the 2003 Oaks, and Regime won his Derby trial well at Sandown..
"Martin has ridden an Oaks winner and a Derby winner so he rides the track very well," said Harry Herbert, racing manager of the Highclere Thoroughbred Racing syndicate, which owns Regime.
"Regime will go to Epsom on Thursday with Martin on board to have a spin around Tattenham Corner.
"We think he is going in to the race underrated as we have always thought the world of him. He ran a big race in the Goffs Million and might have won if he was on the other side."
"The favourite will be a very tough nut to crack but hopefully we will be in a position to test him."
Dettori will ride the favourite, Authorized, who was an impressive winner of the Dante Stakes at York last week.
The Italian-born jockey will be having his 15th ride in the world's most famous Flat race but is still seeking his first victory.
Spencer's French suspension comes on top of a two-day penalty imposed in Britain, which he appealed against unsuccessfully to the Horseracing Regulatory Authority last week.
It ruled him of action on 23 and 24 May, but the Irish rider will now have to sit out all meetings held between 25 May and 3 June.