THE cobbled streets around Stirling Castle have borne the imprint of history down through the centuries. But today the natives of the medieval royal town are in for a complete revolution when the aerodynamic carbon fibre machines of modern-day time-trial riders attempt the impossible in a race against the clock in the opening event of the nine-day Round-Britain Prutour.

The fastest men in the field of 108 will aim to clock up a time of just over five minutes for the short and testing route which begins in the town centre's Murray Place at 11.01 with riders taking off at one-minute intervals.

Race favourite Chris Boardman, the world record holder at 4000 metres on the track, will use every ounce of energy to propel his strange-looking bike around the 2.6 mile prologue course.

He comes to the race unhappy with his form and admits to being a bit nervous with the label favourite. Like many of his team-mates in the Gan squad he was hit by the flu virus which swept through the pro ranks in February and March. He may not be quite race fit, but given his dedication to fitness and preparation, the 29-year-old Olympic champion should win the opening prologue. After all he has won two stages in the Tour de France.

Victory in Stirling should give him a great chance of going on to win the red jersey of overall winner in London.

His No.1 rival is sure to be Slava Ekimov of the US Postal team, another time trial expert and former world pursuit champion.

The 33-year-old Russian is a dangerous performer in time trial racing and has an explosive finish. He won a stage in the Tour de France in 1991 and other stage victories include Tour of Switzerland, Paris-Nice, Dauphine Libere and Tour of Luxembourg.

The biggest threat to Boardman and Ekimov could come from two other members of the US team, Jean-Cyril Robin and Jonathan Vaughters, who is his country's time trial champion and is a natural climber who will find little difficulty in the hills of England and Wales. Another highly-rated rider is Australian Neil Stephens. Blond-haired Stevo, who has been a pro for 14 years, joined Festina, another of Europe's top outfits, from Once last year and helped Frenchman Richard Virenque take second place overall in the Tour.

The Prutour is sure to turn up some surprises as it winds its way through Britain. There are 18 six-man squads with international teams from Great Britain, Scotland, England, Ireland, Wales, Denmark, Holland, and Australia, New Zealand and South Africa.

Scotland, led by former Motorola professional Brian Smith from Paisley, see the race as a good testing ground for the Commonwealth Games. Their team is Smith, Richard Moore, Gary Paterson, Stephen Russell and Drew Wilson and Andy Matheson.

Tomorrow, the race switches to Edinburgh Castle for the start of the 129-mile first road stage which passes through Galashiels and Jedburgh, before heading over Carter Bar and on to a circuit finish in Newcastle.

Stage two, 105 miles from Gateshead to York, is the first really hilly day with Category One climbs at Westerdale and Rosedale Chimney. Stage three, Manchester to Blackpool, has climbs at Holme Moss and Waddington Fell, but a bunch sprint finish on the Blackpool prom looks likely.

Next is Chester to Nottingham, then Birmingham to Cardiff, Chessington to Medway and the finale, a 50-mile circuit around Holborn, London, where sponsors Prudential have their headquarters.

qTHE two-day Tour of the Kingdom gets under way today with a huge entry of 120 riders from all over Britain, including last year's winner, Andy Lyons from Cannons Pro CT. Scotland are well represented with club and national riders.

The young squad of Gregg Imlah, Martin Lonie, Paul Rennie and Craig McQueen are on national duty. Stage one takes the riders from Dunfermline to St Andrews, then St Andrews to Falkland, and tomorrow, the Leven stage.