Format will be aiming to give Waterhouse a sixth VRC St Leger success following wins to Hippopus, Order Of The Sun, Runaway, Transact and Sacramento, the last three in partnership with Bott.
He is striving to become the first product of champion stallion Frankel to win the race that is four years older than the Melbourne Cup and is out of a mare who has experienced success at the highest level at Flemington, albeit over a much shorter trip.
Format is out of Fastnet Rock mare Nechita, winner of Australia's premier speed test for three-year-olds, the Group 1 Coolmore Stud Stakes (1200m), in 2012.
She started her broodmare career in Europe after being purchased by Coolmore for $1.55 million in 2013.
Her first five foals to race were all by Galileo, including Group 1 The Metropolitan (2400m) placegetter Harpo Marx, Group 2 King Edward VII Stakes (2414m) placegetter Artistic Star and Forebearance, a Group 3 winner over 2414m, which gives Bott confidence ahead of the St Leger.
"He should appreciate the trip," Bott said.
Format came up with barrier eight in the 12-horse VRC St Leger with Ben Melham to take the ride.