Tony McCoy could make the bookies tremble again

You would think that finding the winner of the Grand National is enough of a puzzle for punters. Now the ever inventive bookies have gone a stage further by opening a market on the identity of the horse who will go off favourite in the world's greatest jump race on Saturday afternoon.

Only a handful can be seriously considered and none has to get round. So it should be a bit easier than finding the winner. Yet strange things happen in the betting world in the final hour before this most compelling of sporting occasions.

Four years ago Monkerhostin's odds tumbled from 25-1 to 8-1 joint favourite after a sustained punt. He had no obvious claims for glory in the form book and was out of the race before they had gone a mile.

Last year there was a late whirlwind gamble on Don't Push It. Most bookmakers were happy to lay 20-1 when proceedings began. By the time of the start of the race, his odds had halved to 10-1 equal favourite and those involved always looked like collecting before Tony McCoy brought him home to universal acclaim.

This year, Ruby Walsh's mount, The Midnight Club, heads the market at 2-1 to start favourite with Sir Alex Ferguson's What A Friend (4-1) second best.

Now there are bound to be plenty of once-a-year punters ready to pin their faith in Fergie's luck at Liverpool, though he will struggle to follow the action while in charge of Manchester United's home game against Fulham. But it wouldn't be the greatest shock if the Scotsman used his current touchline ban to keep up to date with the action at Aintree by telephone from his unnacustomed position in the stands.

The big bookies have reason to fear victory for What A Friend. But they might have made a costly mistake in pricing up Don't Push It at 11-2 to start favourite with the peerless McCoy in the saddle once more. He was already a household name before Don't Push It helped him end an uncomfortably long drought in this most famous of races. The handicapper has generously raised him only 5lbs for that comfortable success and the word from Jonjo O'Neill's stables is that the horse is in sparkling form again.

Bookmakers tremble when Don't Push It's owner JP McManus steps into the betting ring. He is the biggest player in the game and if he opens his shoulders on Saturday, the sheer volume of his bets will ensure that his horse starts favourite.