Right place, right time

Do you recognise this church? Are you sure? Fair enough; it is a bit obscure. It is Dials Methodist Church, Gray Court, South Carolina. While you may not have known the name, the shape is probably familiar. A steeple rising from behind a pediment (that's the triangular bit) supported by columns and preceded by steps is a classic of American church design, repeated in thousands of small towns and big cities.

While these unremarkable churches are endlessly varied, they have one common ancestor; and it isn't American.

St Martin-in-the-Fields is one of London's finest buildings; and one of its most overlooked. Sitting in the corner of Trafalgar Square, it is the square's finest piece of architecture but without the celebrity sheen generated by lions, fountains, Nelson, the National Gallery and the fourth plinth. Goodness, even Admiralty Arch has acquired a certain grotesque glamour since becoming known for John Prescott doing the unthinkable with his secretary Tracey Temple.

While few Londoners now stop to admire St Martins (and very few could name James Gibbs as its architect), it was once the most talked about building in London. Gibbs combined the classic Italian temple front (columns and pediment) with an English baroque steeple. No-one had done this before, and Londoners (always conservative about church design) were sceptical anyone should have done.

However, if he had wanted architectural influence in what was to become the world's largest Christian country, he was building at right time. At the start of the 18th century, the population of the English colonies was 275,000 and the largest city, Boston, had a population of 7,000; a tenth the size of today's Walthamstow. St Martins was completed in 1724. By the end of that century, the newly-independent United States of America had a population of 4 million, and the radical design of Gibb's new church had spawned hundreds of imitations.

It's easy to take Trafalgar Square for granted, but don't. I was reminded of this on Sunday, at one of our family Christmas traditions. Every year, St Martins holds a blessing of the crib in the centre of the square. Standing in the cold and dark singing carols by lanternlight, surrounded by the noise and mundanity of the modern city, there is a magic in the layers of history to be found in the buildings of a square built for a long-lost empire. The names of some of the most prominent buildings speak directly to this history (South Africa House, Canada House, Uganda House) but so, much more subtly, does St Martin-in-the-Fields.