Londoners: Look down, and worry ...

When you walk around London, beneath your feet are layers and layers of history. There are also, so we're told, millions and millions of rats, massive but leaking Victorian sewers, and more than the odd plague pit. These are the aspects of the city that captured the imagination of Stephen Smith, and in his Underground London: Travels Beneath the City Streets he seeks to find all of these and more.

He's a journalist, and has the journalist's knack of talking his way into the oddest places and situations, from the crypt of St Andrew's Holborn as workmen clear out a noxious mix of bodies, coffins and maybe the odd anthrax spoor, to a river boat from which a small boy is being dangled by his ankles while he beats the water with a cane. (No, we're not talking hideous Satanist ceremonies there; rather an old City tradition.)

He starts out in the Tube - noting that in 2002 a new record for visiting all 272 stations was set (19 hours, 18 minutes and 45 seconds) - and ends up at the Thames Barrier, (the definition of underground sometimes being rather loose), with a nasty reminder that the foundations of the city might be less secure than they seem, its use having risen from only nine times between 1982 and 1991, to 14 times in one week in 2002.

Smith writes with brio, if sometimes self-conscious brio. He's setting himself up as a character, and that "personality" side of his writing, like those TV archaeologists who leap around like Archimedes on his best day just because they've found a pot sherd, can get annoying. But the writing moves fast enough that this is only a momentary irritation.

The research is somewhat scanty in places, but its breadth is its redeeming feature. So a visit to Berry Brothers, the "Italian warehouse" set up by the Widow Bourn in 1698, opposite the royal tennis court in St James's Palace provokes reflections on everything from Pitt the Younger and Napoleon III weighing themselves in the basement to a 1991 cause celebre when six Barclay Bank employs got themselves into hot water by spending £44,000 on one lunch. Then he joins in a wine tasting at the firm (that's now their specialty):

"To the accompaniment of the silky, ship's-screw noise of air conditioning, tipplers circulated among damask-draped tables, accepting the equivalent of an optic or so of the ruby-coloured stuff from the Berry staff. The punters glugged and spat - or swallowed, at their discretion - before jotting down their thoughts on the ports. The illusion that these smartly dressed men and women were fastidiously keeping dance-cards reinforced an impression that the evening belonged to a bygone age."

The focus on being below soil produces some surprising results. I don't know that under the Merton Abbey Savacentre - in the southwest corner of the Tube map - there is indeed the remains of an abbey - one that once rivalled Westminster in size and wealth. Nor did I know that fragments of Henry VIII's tennis court survive in the Cabinet Office, and can be viewed on the London Open House weekend. (Something got the diary there.)

As a potted introductory history to the city for the neophyte, or as a reminder to a jaundiced veteran that there are still many things to discover, Underground London digs in nicely.