A crowd of 80,000, more than turn up on race day at some other circuits, had been expected to watch the practice sessions and Silverstone authorities warned spectators the day before of likely delays due to waterlogged campsites.

In the end, on what was forecast to be the wettest day of the British summer so far with the possibility of a month's rainfall in the space of 24 hours, it turned out worse than feared.

"It's a nightmare," said Katie Tyler, Silverstone's head of communications, as steady rain swept the circuit and traffic clogged the roads outside.

"That is what is so frustrating, that we'd almost got over the hangover of 2000. It seems we're about to go through it again."

In 2000, when the grand prix was held earlier than usual in April, thousands of ticketholders were unable to see the race after rain turned parking lots into quagmires and created traffic chaos.

Tractors had to pull cars out of deep ruts and public vehicles were banned altogether on the Saturday when car parks were closed to preserve them for race day.

While the grandstands were impressively crowded on Friday, and an army of fans braved the elements around the former airfield circuit, witnesses reported traffic at a standstill well into the afternoon.

One local said it had taken him two hours in the morning to cover a journey that normally takes 10 minutes from door to door.

A Reuters reporter said some corporate guests had abandoned their bus and walked the last miles into the circuit to have a chance of seeing a Formula One car in action, and organisers faced questions about ticket refunds.

SERIOUS PROBLEM

"We know we've got a problem, we know it's serious," said Tyler. "We've the best people on the job, and we're doing all we can, with people discussing what we do tonight and tomorrow.

"One of the key decisions is getting the people waiting to get into campsites relocated, and then how we get the campers on to site tomorrow morning."

Much has changed for the better since 2000, with the circuit spending more than 1 million pounds a year on preparing and managing car parks and trying to ensure the traffic flows smoothly.

For this year, with more than 125,000 expected on race Sunday, an extra mile of filter drainage has been put in and 1,100 tonnes of hardcore added to car parks but the sheer number of people trying to get into campsites without pre-booking, coupled with the weather, has been hard to handle.

Tyler said people were being turned away from private campsites because of reduced capacity due to ground conditions while at the main official site, camper vans were having to be towed in one at a time.

The British summer, always unpredictable, has been particularly damp this year - the country had its wettest April in more than a century - with flash floods in places. The forecast is for rain throughout the weekend.

Camping is a big part of the weekend at Silverstone, surrounded by fields in the heart of England, with many drivers staying on site in motorhomes in close proximity to the fans rather than retreating to luxury hotels.

At its best, with the sun shining and the whiff of barbecue smoke in the air, it is one of the most inclusive races of any on the calendar. Providing one can get in. (Additional reporting by Keith Weir, editing by Alison Wildey)

• A Permanent Economic Emergency