The security services have been privately predicting it for weeks. John Reid warned only yesterday that Britain was under its most serious threat since the Second World War.

Today we learnt what they had been hinting at. An outrage of unimaginable proportions that could even have matched 9/11 in the sheer scale of the horror involved.

Tony Blair must now be wondering yet again why he even bothered to plan a holiday to Barbados in the middle of August. First, he had to join his family almost a week late because of his close involvement in negotiations on a Lebanon resolution.

No sooner had he arrived than things started going wrong at the United Nations in New York and he had to embark on a new round of chats with leaders, including President Bush.

He was told late last night, Barbados time, that moves to disrupt the biggest terrorist plot against British citizens were about to be launched. He took the opportunity of his talk with Mr Bush to brief him on the operation about to take place in London and elsewhere.

Yet again the holiday jinx had struck the Prime Minister. Hopes of a quiet August in which it would hardly be noticed that John Prescott was allegedly in charge of the country had long ago vanished.

On this occasion, however, Mr Blair was missing out on the chance to hail the work of Britain's police and security forces, under a cloud since the Forest Gate raid on suspects failed to produce results.

Last year Mr Prescott was in charge as the Cabinet's Cobra committee met regularly in the wake of the July 7 attacks on London.

Today it looks very much as if John Reid is in charge of the Government, starting from this morning at a dramatic press briefing when he announced that the country was on "critical" alert.

It was the Home Secretary who swiftly chaired two meetings of the Cobra committee, one late last night and one this morning to hear the results of the pre-emptive action taken by the police and security services. But Mr Prescott was also busy, in talks with Muslim organisations.

The Opposition parties have been swift in their praise of the security services and the Government response. For the time being the Labour rebels over Lebanon have quietened. But they have not gone away and Mr Blair and his ministers will wonder what the rest of August holds for them.

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