The Cheltenham Gold Cup hero and 6/1 fav for the big race is set to attract tens of millions of pounds of bets.
David Williams of Ladbrokes said: “If the nation decides to trust in McCoy we could be staring down the barrel of some record-breaking liabilities on Synchronised.
“McCoy’s win on Don’t Push It in 2010 was one of the costliest days in our history but it could pale into insignificance if the mega money arrives for Synchronised.”
And with Ruby Walsh’s sister Katie having her first National ride aboard Seabass, the bookies suspect that the Irish-trained 9 year old could be the “housewives’ choice.”
“With half the adult population looking to have a flutter, Katie will have an army of fans. It would be a fairytale if she cooked the bookies with Seabass” said Williams.
Over £300 million of bets will be wagered on Saturday in the biggest day of betting of the year. Earlier in the week, Ladbrokes reported West End Rocker and Shackalackaboomboom to be attracting plenty of attention in the 40 runner field.
Ladbrokes latest betting on the Grand National: 6 Synchronised, 9 Junior, 10 Cappa Bleu, 10 On His Own, 11 West End Rocker, 12 Ballabriggs, 12 Giles Cross, 14 Seabass, 16 Killyglen, 16 Chicago Grey, 16 Sunnyhillboy, 16 Treacle, 20 Becauseicouldntsee, 20 Organised Confusion, 20 Shackalackaboomboom, 25/1 bar