In December 2002 Matron submitted an old system and proffered that it was unlikely to work in the present day.
For some afternoon fun I ran it through the afternoon cards and came up with some interesting selections but to try and bring it up to date I did filter my winning at race class suggestion.
Thirsk
4.05 Just the tonic 8/1 3 places 1/4 . . . LOST
4.40 Crocodile Bay 5/1 3 places 1/4 . . . LOST
620 Gap Princess 14/1 4 places 1/4 . . . . LOST
Ascot
5.00 Junior 8/1 4 places 1/4 . . WON 17/2 
Handicap races, working upwards from the bottom of the card select the first horse with 1 LTO (my addition is the nominated horse should have won at todays race class)