Tony Blair cancelled meetings for crisis cabinet

Many claim that was a mistake because he painted himself into a corner and left the protesters no face-saving escape route. His supporters, however, insist he had no other option.

Having seen what happened in France, and the bad press the Jospin government received for its apparent cave-in, Mr Blair is determined not to go down the same path.

Public support

It is now inconceivable that he will back down and give the protesters what they want - that would be seen as a fatal weakness and would dramatically undermine the government's standing.

And, in any case, if there is one thing the prime minister prides himself on it is his Thatcheresque determination never to be swayed by intimidation from any pressure group.

But he clearly does not want the dying days of his first government to be dominated by pictures of police breaking up demonstrations and the violence that could so easily follow. But that is looking increasingly likely.

Probably the crucial factor in the crisis is whether the demonstrators manage to win public opinion over to their side.

While the loose grouping of farmers, taxi drivers and truckers leading the protests currently has a degree of public support, it is clear that support is fragile.

There is nothing like the sympathy generated by the miners' strike and - while many motorists feel they are being particularly targeted by the government's tax regime - there are no signs of the sort of widespread anger generated by the poll tax.

And when the pumps do finally run dry and people are unable to get to work or take their children to school it is highly likely the support will evaporate.

It now, therefore, seems highly likely that the prime minister will use his contingency powers to break up the protests.

It is also possible that he will offer some sort of olive branch about essential users in a bid to allow the protestors to save face.

It will probably be the most significant decision he has ever made as prime minister.