Petrol: Army is put on standby

Troops will take the wheel of tankers if ambulances, fire engines and police cars start to run out of fuel.

Emergency powers will also allow police to surround depots to protect essential supplies.

As Gordon Brown condemned the strike, Downing Street said the Government's response would be proportional to the seriousness of disruption.

One London filling station ran dry this morning, soon after the drivers walked out in a pay dispute.

Ministers believe they can hold out to the end of the four-day strike without calling on Army drivers or a major police operation. But the fear is that the 500 strikers could be joined by other groups, such as the protesters against high fuel taxes who brought the country to a standstill eight years ago.

The military will not serve filling stations and drivers were today urged by the AA not to waste a drop of fuel.

Business Secretary John Hutton, the Cabinet minister in charge of the emergency response, said contingency plans were in place to reduce disruption. He added: "Our advice to motorists is just to buy the fuel they need."

Forecourts at Shell garages across the capital said that business was up and many were hit by queues as drivers filled up.

Retailers and the Government called for "restraint" and said there was plenty of fuel to go round.

The Petrol Retailers Association said there was no lack of fuel as long as motorists "bought normally". Tanker drivers for Shell, which provides 10 per cent of Britain's petrol needs, walked out at 6am for four days of action. Union leaders warned fuel would start to run out "almost immediately" and all Shell's forecourts would be affected within 24 hours.

Pickets at terminals around the country were manned by hundreds of trade union members seeking a pay rise.

The first impact was felt at the Shell garage in Bayswater Road as it ran out at 6am. Duty manager A Vikmaesan said the last delivery was yesterday morning, but a rush of customers had emptied supplies. On the forecourt was David Lewes, 57, a corporate lawyer from Notting Hill. He said: "I do have sympathy for the staff who are striking. But I'm in a rush to get to a meeting and I am going to have to drive round looking for another petrol station."

Government officials said there was no reason for Londoners to fear the pumps running dry.

They said pickets were not being allowed to block the road at the Coryton refinery in Essex, which is the main supplier to the capital. That meant that although drivers serving Shell stations may not work, they would not stop deliveries to other brands.

There was no disruption at the West London Terminal, which is supplied by a pipeline and serves Esso tankers.

"London drivers need not worry because if their Shell station runs out there should always be a filling station round the corner with supplies," said an official.

However, Shell pumps in Fulham Palace Road and Brompton Road and even the BP garage at Hammersmith flyover were much busier than normal.

Emily Blaylocke, 32, an interior designer filling up in Fulham, said: "I'm meant to be driving to Nottingham this weekend to see my parents and I might have to put that on hold in case I get stranded."

The Shell station manager at Brompton Road said he was unsure how long his stocks would last - but almost certainly not for another 24 hours.

Anastasia Brohin, 39, from Chelsea, filling up her Range Rover, said: "I have to fill my car at least every other day. I queued for nearly 20 minutes today." Mike Townsley, 32, a plumber driving a white van and filling a spare canister, said: "It's always better to have a bit extra. If the strike goes on for four days you know everywhere's going to be empty by Sunday. If there's an emergency I'd rather be safe than sorry."

Motorists denied they were panic-buying and ignoring official advice but said they were simply being cautious.They complained that the dwindling number of pumps in central London meant they were having to drive long distances to fill up.

Assaf Bind Hadi, 36, a project developer driving a Ferrari in Brompton Road, said: "I'm filling my car but I won't be able to get through four days without filling it again. They should give priority to people like me who need it for work."

Officials from the Unite union and managers from two firms which deliver fuel to Shell garages held more than nine hours of talks yesterday but they broke down last night. The pay row erupted after the union claimed workers are paid the same now as in 1992 - just under £32,000 a year.