Aerial footage of protest by lorry drivers
Hundreds of hauliers have demonstrated in London against rising fuel prices.
Up to 230 lorries parked in a specially closed section of the A40, while others, escorted by police, drove into the heart of the city.
The drivers want a fuel tax rebate of about 25p in the pound, claiming many are being driven out of business.
The government says it might postpone future fuel tax rises, but warns that a cut in current duty will hit spending in other areas of the economy.
The Road Haulage Association (RHA), which backed Wednesday's protest, said that the demonstrations would be repeated if the government refused to listen to its demands.
A spokeswoman played down charges that fewer drivers than expected had responded to the protest call, saying "times were hard" and many drivers could not afford to take the day off.
Other drivers warned of future "wildcat" actions - like the haulage protests in 2000 which closed petrol stations throughout the UK.
Meanwhile the government defeated a challenge to its plans to raise vehicle excise duty on the most polluting cars.
With the average price of diesel calculated at £1.32 per litre, hauliers say this leaves them with fuel bills of up to £1,000 per week for a typical articulated lorry.
Many complain that they are being driven out of business because of competition from drivers from other European countries, where fuel is around 25p a litre cheaper.
The RHA says the entire UK economy is at risk from rising fuel costs.
National RHA chairman Andy Boyle said: "If ever there was positive proof that ours is an industry in crisis, then this surely must be it.
"For many, today will represent a last-ditch attempt at making their voice heard."
The government looks likely to reject outright calls from hauliers for an "essential user rebate" of between 20 and 25p.
One trucker explains why he is protesting
It blames the rising international cost of oil for the fuel rises, but says it may postpone future plans to raise duty by 2p a litre.
A Treasury spokesman said: "The chancellor postponed the planned increase in fuel duty in April because of concern about high fuel prices.
"He has said he is willing to postpone it again in October if he judges it to be right."
He added: "There is no tax windfall from higher fuel prices.
"Any additional tax revenue is offset by a reduction in spending in other areas of the economy and reduced consumption of fuel due to higher prices."
Wednesday's protests began with a gathering of lorry drivers at Medway Services in Kent. The drivers then set off for the capital along the M2 motorway.
A second convoy set off from Gateway Services on the M1.
With part of the London-bound A40 closed during the demonstration, police estimated about 230 lorries had arrived by 1330 BST - fewer than the 300-plus vehicles expected.
Traffic in and out of the city remained relatively unaffected, with no serious instances of disruption reported.
During the morning, police on motorcycles escorted groups of 20 lorries into the centre of London, where drivers and their supporters had gathered for a demonstration outside the Houses of Parliament.
Peter Caroll, owner of Seymour Transport and member of lobby group TransAction 2007, told the BBC that British hauliers could not compete with foreign rivals.
He said: "We are under mortal threat. The UK road haulage industry is not in trouble, it is facing a catastrophe."
Driver Mike Wright, 61, from the Heathrow-based Roy Bowles company, said "wildcat protests" could be the next step all across the country.
"They will block every motorway in the country and then the government might listen," he said.