As Presidents Bush and Putin signed their historic arms pact, Tony Blair presented three history books to 18-year-old Euan at the London Oratory School’s patronal festival.

His were two of 123 prizes given out after High Mass at London Oratory Church, full of fine music, Latin and a sermon by Cardinal Cormac Murphy O’Connor, Archbishop of Westminster, who found himself swathed in clouds of sweet incense.

Proud mother Cherie, a Roman Catholic, also attended and, as on many other school occasions, was armed with her camera.

Mr Blair read the first lesson - from the letter from St Paul to the Philippians, leading off with one of Mrs Thatcher’s favourite words:

“rejoice”.

Euan - famously reprimanded by police after being the worse for drink in London’s Leicester Square after celebrating the end of his GCSEs - won an award for public speaking.

There was another for being one of four deputy heads of school at the Oratory, one of the best-known state schools in the country.

There was the briefest of “well dones” from father to son as he handed over the books, but Mr Blair beamed.

There were gifts, too, for Mr Blair from the school - a leather-bound edition of The Stones of Venice by Ruskin, which had sat perilously close to a book called The Art of Illusion.

For Mrs Blair there was a bouquet of yellow and orange flowers delivered by the tiniest of schoolboys. “Go on, give me a kiss,” she said to the clearly bemused little boy, who duly obliged before being led away.

For headteacher John McIntosh it was a memorable occasion, not just for the presence of the Blairs. It is 25 years since he became head of the Catholic school, rarely out of the news since opting out of the control of the London borough of Hammersmith and Fulham in 1989.

Seven years later, Mr McIntosh confirmed his maverick reputation when he persuaded the Conservative government to give him a grant to set up a junior house of boys aged seven to 10 for specialist music education.

In June 1996 he was awarded an OBE for services to education. A month later, Mr McIntosh threatened to make the school fee-paying if Labour were elected.

And then in 1999 he embarrassed Labour on the eve of its party conference by asking parents for pound;30 monthly covenants because of financial difficulties.

But last Friday, past differences were put aside as Labour luminaries mingled with Tory grandees.

Former minister Harriet Harman, whose son Harry Dromey was head boy last year, sat alongside the Blairs’ security man, who gamely sang along to the Latin words of the school song. Only minutes before the Blairs arrived, a clearly embarrassed Ms Harman had to retrieve a ringing mobile telephone from her handbag.

Across the aisle was Baroness Blatch, Conservative peer, Sir Robert Balchin, godfather of the grant-maintained movement, and Tessa Keswick, director of the Centre for Policy Studies.

Christine Whatford, director of education at Hammersmith and Fulham, sat alongside Mr McIntosh’s parents.

And for the boys who did not win prizes there were words of encouragement from the Cardinal. The only award he won while at school was third prize - in religion.