He postponed his holidays because of the crisis in Lebanon...

According to the BBC here:

"Heathrow Airport has been closed to all incoming flights that are not already in the air, following a police anti-terror operation.
British Airways said it had cancelled all short-haul UK and European inbound and outbound flights to and from Heathrow until 1500 BST."

and here:

"The Home Office confirmed there had been three meetings overnight and on Thursday morning of the Cabinet's emergency committee, Cobra, chaired by Home Secretary John Reid, to discuss the terror alert .
A spokesman for Number 10 said Tony Blair had briefed US President George Bush on the situation during the night."

Surprising, therefore, that the Prime Minister felt able to fly off to the West Indies, leaving the country leaderless in this time of crisis.