By Brian Wheeler
Political reporter, BBC News, in Westminster
Spurred on by horn blasts from trucks and buses thundering towards Parliament Square, Peter Caroll, of lobby group TransAction, told the placard-waving crowd of truckers that their whole industry was facing extinction.
The protesters fear their businesses will be wiped out
"If the government does not listen they will find people so desperate - they will find people doing things that we could not condone, but we would find hard to condemn," said Mr Caroll.
"It breaks my heart when I meet people that are having to remortgage their homes to stay afloat. It is commercial slaughter on a massive scale."
Hundreds of road hauliers from across the UK had gathered outside Parliament to protest against soaring fuel prices.
Many fear the businesses they have spent years building up will go down the drain unless the government acts.
And their leaders warned Prime Minister Gordon Brown he could be facing a repeat of 2000's fuel protests which nearly brought the country to its knees.
Most of those taking part in the protest - timed to coincide with the weekly prime minister's questions session - were the owners of small family and medium sized family firms, with less than 100 trucks.
They operate on tighter profit margins than the corporate road haulage giants and found it less easy to pass on price increases to customers.
Sandy McCracken, who had travelled down from Rigside, in South Lanarkshire, in a kilt made of the family tartan, feared his business would not survive: "We are really struggling."
His banner read: "We're hauliers. We have had it tough and now we have had enough."
He said his fuel costs had gone up by nearly £1m a year for his fleet of 50 trucks and his drivers - who he thought of as "family" - were also feeling the pinch of rising prices at home.
"I don't think we have been as militant as we were in 2000. But there is more anger about this time. I don't think people can afford to stop this time, to take part in protests."
The police were also using "scaremongering tactics" against likely troublemakers, he said.
"They are targeting the people that are going to be militant."
His wife, Pat, said: "This is the last ditch for all of us. It is just so soul destroying.
"For years and years people have built their businesses up, working long hours and we are getting no encouragement.
"The country would grind to a halt without us. If you bought it, a truck brought it."
Like many of the hauliers I spoke to, Pat was angry about politicians using the environment to justify fuel price increases.
Rising prices will only succeed in wiping out the British road haulage industry - and open the door to firms from mainland Europe, who were already taking advantage of cheaper fuel prices, they argue.
"All this crap about the environment is just a load of rubbish.
"Foreign trucks that come over don't buy fuel here, they don't pay road tax. The government has no jurisdiction over them. At least at the moment we are abiding by British laws."
Barry Jordan, of Sunningdale, Berkshire, said the fuel costs for his firm - which he started 20 years ago "with nothing" - had gone up from 30% to 40% of his turnover.
"Road hauliers are not militant. We are mainly conservative but we have to make our voices heard.
"We are talking about the survival of an industry here. We are not just complaining because we haven't had a big enough pay rise."
He also felt angry about the way the green argument had been manipulated by politicians.
"I have an environmental conscience, as well as a commercial conscience, but we do not deliver goods by rail we deliver them by road.
"The country needs the industry and the industry may not survive."
Robert Wilcox, who operates 70 trucks from his base in Bath, Somerset, said all the hauliers wanted was fuel prices brought into line with the rest of Europe - or at least an end to price fluctuations.
"We are not asking the government to give us cheap fuel. What we need as an industry is stability," said Mr Wilcox, whose firm Massey Wilcox was established in 1954.
"If it goes up to £10 a gallon, let's have it at £10 a gallon for more than a few days."
The government was cashing-in on high oil prices through VAT - another common theme among the protesters - and all they wanted was a fair slice of the profits, he argued.
"I hope they listen to us. They are making more money than they planned to make out of fuel.
"What we are saying to them is - you are making a margin out of us, can you use some of that money to control some of the prices.
"What we would really like is to have our fuel prices in line with Europe."