Three horses since the turn of the century have completed the Great Voltigeur ad St Leger double in the same year and six more are attempting to follow suit this year.
Main Sequence finished second to Camelot in the Epsom Derby earlier this season and looked slightly unlucky when failing to get a run in fourth at Longchamp last time.
He is the 9/4 favourite to win the Great Voltigeur and 20/1 to complete the double of also claiming victory in the St Leger.
Sir Henry Cecil has two of the Great Voltigeur field and it is Thomas Chippendale that is the shorter price to triumph at York at 7/2.
Thomas Chippendale won the King Edward VII Stakes last time, beating stablemate Noble Mission on that occasion.
However, Noble Mission has reportedly come on at home since in terms of his attitude and is capable of exacting revenge for this loss.
Noble Mission is 4/1 to win the Great Voltigeur and more than most should appreciate the step up in distance from 1m4f to 1m6f for the St Leger.
Frankel’s brother can be backed at 28/1 to step slightly out of the shadow of his sibling by winning both the Great Voltigeur and St Leger.
Mahmood Al Zarooni is another trainer with two chances of potentially completing the double.
Encke has never been outside the first two in all five of his career starts, while Royal Ascot victor Energizer is preparing for his first run for the yard since being purchased from Germany.
It is 9/2 that Encke wins at York, with Energizer the outsider of the six runners at 8/1.
Meanwhile, the former is 25/1 to win the Great Voltigeur and St Leger, with Energizer 40/1 to do the same double.
The final alternative is Thought Worthy from the John Gosden yard, which was responsible for the last big-race double with Lucarno in 2007.
Thought Worthy is 6/1 to win the Great Voltigeur and also 40/1 to make it back-to-back successes at Doncaster in the St Leger.
All Odds and Markets are correct as of the date of publishing.