Grand National overround stressed the need for openness with the SPs

The annual rip-off of the unenlightened punter eclipsed previous records at Aintree last Saturday when the starting prices for the Grand National reached an alarming 155% overround.

they want must pay out for Every pound put into Them. With Standard and Poor bookmakers Is there any kind of limit set on how high the overround Can Get?

Having been 20-1 on the morning of the race, the winner, Don't Push It, contracted markedly in price in the final minutes before the off and SP punters were paid out at 10-1. He was returned at more than 18-1 on Betfair's own starting price system and more than 14-1 on the Tote.

Other horses were also the subject of dramatic price collapses, with the market apparently failing to compensate and lengthen the odds of the other runners.

This amounts to an overround of below 1.5% per runner, so there have been worse cases of SP punters getting taken for a ride. Last October a 13-runner handicap at Kempton attracted attention when Giant Sequoia was returned the 4-9 favourite, despite being widely available at odds-against on Betfair. The overround on the race was 141% – over 3% per runner.

The Grand National is a once-a-year bonanza for bookmakers. Ladbrokes take five times as much money on the race as they do on the Derby, the second-most popular betting race of the year.

It is "common business sense", the PR representative for one bookmaker put it yesterday, that in the final minutes before the race the major off-course firms would want to hedge against their liabilities. There should be no suggestion that they are acting improperly in doing this.

Both Ladbrokes and William Hill confirmed yesterday they had backed Don't Push It on-course.

The percentage of punters who strike bets at starting price has declined markedly in recent years – perhaps unsurprisingly given the way the overround increased markedly in favour of the bookmaker after the most recent (2006) reforms to the formula by which the SP is calculated.

However, Ladbrokes still estimate that 40% of their shop punters (far more than online or on the phones) were still taking starting price on their Grand National bets and if, as their own post-race publicity claimed, Don't Push It was the most popular horse for the once-a-year punters who pinned their hopes on Tony McCoy, it does not take a mathematical genius to work out that shaving even a couple of points off the winner's SP would offer the big firms a considerable saving. There are two greater concerns: firstly, that the odds on the weaker horses in the betting failed to drift at all; and, secondly, the idea that those placing the late bets seemed to know which of the on-course bookmakers were among the 24 selected for the sample which formed the starting price.

"The identity of the bookmakers used for the sample is confidential and not passed on to anyone other than those involved in the monitoring of the starting price," said Jim Donnelley, the company secretary to the Starting Price Regulatory Commission.

Perhaps, in that case, the bookmakers who are used to form the SP need to be subject to greater rotation. One boards layer yesterday claimed to have been offering 14-1 on Don't Push It at the off, without attracting much business. But then he was not part of the sample.

Increased transparency might not solve the inadequacies of the SP system but it could still provide an answer to some questions. The technology for a transaction-based system, using data from bets actually struck, is still an improbable dream – the SPRC lacks the funding or authority for its implementation in any case.

But the information is available to show how every SP, whether for the Grand National or any other race, is calculated. The data screen used by the SP validator to monitor – in real time – the prices shown by the selected bookmakers displays every price change, every layer's overround and exactly how each starting price is reached.

In the interests of racing bookmakers should agree to this information being made available online for all to see. Donnelley said yesterday that it would be discussed at the next SPRC board meeting.