The promotor of the British Grand Prix secured the future of its race yesterday by proposing an unprecedented £3.2 million sterling gamble which has been accepted by the sport's world governing body.

Octagon Motorsports offered to lodge that sum with the FIA as a guarantee that it has solved the access problems which have blighted the past two grands prix at Silverstone, leaving thousands of fans fuming in traffic jams.

Further details and terms of what is described as a "performance bond" will be agreed between Octagon and the FIA's lawyers in the next week.

If the arrangements for the race do not come up to standard, the money may be forfeited.

Before yesterday's world motorsport council meeting in Monte Carlo where the future of the race was decided, however, the seriousness of the situation worried the British Prime Minister Tony Blair so much that he put in a reassuring call to the FIA's president Max Mosley.

Following the meeting Mosley said: "After the broken promises of recent years from the organisers of the British grand prix, the FIA has now received binding commitments that the chaos experienced by motorsport fans in recent years will be properly addressed in time for next year's grand prix."

In addition to persuasive support from the prime minister's office, the Secretary of State for Culture Tessa Jowell and Minister for Sport Richard Caborn brought their influence to bear on the FIA.

Mosley also received calls from the chief constables of Thames Valley and Northamptonshire and Jackie Stewart, president of the British Racing Drivers' Club, the owners of Silverstone, also lobbied the politicians.