If, at low tide, you stand at the bottom of a flight of steps disappearing into the River Thames to the immediate west of Cannon Street station and look to your left, you might just see a lugubrious trickle of water trailing from an unprepossessing sewer outlet overshadowed by the Victorian railway bridge. This is all that is visible of the Walbrook, a hidden London river, its secret course following the east elevation of the Bloomberg headquarters in the City of London.

Hidden, perhaps, and yet the Walbrook was key to the foundation of London in the AD40s. A tidal inlet of the Thames, it was an ideal river along which to berth ships, and a small port was built here more or less where Sir Christopher Wren’s secretly domed church of St Stephen Walbrook has stood since soon after the Great Fire of London. Walbrook played a vital role in Roman trade, with ships sailing to and from both sides of the Mediterranean and even further to Phoenicia, the ‘Land of the Palm Trees’ stretching along the coasts of what we know today as Lebanon, Israel, Gaza, Syria and Turkey. Founded by Romans, London was a global city of sorts two thousand years ago...[+]