He really is priceless. Other world leaders see the Pope with their advisers and the Vatican's peerlessly punctilious protocol experts, making sure they do not commit the slightest gaffe. But George W. Bush can outwit them all. On the plane to Rome, he was already struggling.

The Pope is addressed as 'Your Holiness'. Roman Catholics refer to him as 'The Holy Father'. But somewhere in the tumble dryer that is the part of the US President's brain set aside for words, the two concepts got tangled and he told Associated Press: 'I think His Holy Father will be pleased to know that much of our foreign policy is based on the admonition to whom much is given, much is required.'

No doubt Pope Benedict, whom Bush later described as 'very smart', was able to deconstruct the rest of the sentence. But before he got down to cases with Bush, the Bishop of Rome, Vicar of Jesus Christ, Successor of the Prince of the Apostles and Supreme Pontiff of the Universal Church had the unusual experience of being called 'sir'. 'It's good to be with you, sir,' said Bush as he sat down. But it was just one of those days for George W. Even the car broke down.

His visit to Rome had been preceded by the biggest security operation this bodyguard's nightmare of a city had ever seen. The Tiber was dragged. The sewers were searched. Squares were cleared and roofs occupied. Yesterday the presidential cavalcade hurtled along its route preceded by a swarm of more than a dozen motorcycles, scooters and even motorised three-wheelers carrying tough-looking armed police riding pillion.

But when it got to Largo Poli, near the Trevi fountain, Bush's car ground to a halt. It remained perilously immobile for a minute and half. The President and Laura Bush were hustled into another car. That was denied by a White House official, who said the reasons for the breakdown were 'unclear'. Just as unclear was how the wide presidential limo could get through the gates of the US embassy. It couldn't. The presidential couple had to walk in.

'But this is how we do things in Italy,' cried a delighted onlooker. At least Bush could take heart from the G8 summit in what, in talking to the German-born Pope, he termed 'your old country'. He described it as 'successful ... good'.

Not everyone saw it that way. Some felt Bush had been spectacularly wrong-footed. Russia's President, Vladimir Putin, suggested that, if America's anti-missile shield was really to protect Europe from Iran and not Russia, the US could use Russian-controlled radar.

The Pope mischievously asked Bush if his talks with Putin had also been good. Glancing at the reporters who were about to be ushered from the room, the President replied: 'Ummm ... I'll tell you in a minute.'