Afternoon tea did not begin on water. The ritual is usually credited to Anna Maria Russell, Duchess of Bedford, who in the 1840s called for bread, butter and tea to bridge the long gap before dinner. Two centuries later that domestic habit has been carried onto a working tidal river, and the thames cruise afternoon tea is the result: a three-tier stand set down on a white cloth while the Houses of Parliament, HMS Belfast and the bascules of Tower Bridge pass the window. The Thames here is tidal. It rises and falls by up to seven metres twice a day. For most of its history the river was a workplace rather than a view. Wharves crowded both banks, and the Pool of London handled cargo from four continents. As the docks moved downstream to Tilbury and the containers followed, the central reaches were left to passenger traffic. The embankments laid over Joseph Bazalgette's intercepting sewers in the 1860s became promenades. Visitors holding thames cruise afternoon tea tickets now cross water that was, within living memory, the preserve of lightermen, stevedores and coal barges. Geography explains the appeal. Between Westminster and Greenwich the river describes a series of wide bends that compress four centuries of building into roughly eleven kilometres of water. Christopher Wren's dome at St Paul's sits almost opposite the Globe. The Shard rises 310 metres above London Bridge station. Tower Bridge, completed in 1894, still raises its bascules for tall vessels several hundred times a year. Canary Wharf stands on the filled basins of the West India Docks, and the masts of the Cutty Sark mark the end of the run beside the Old Royal Naval College. No street route in the capital delivers that sequence in order, which is why thames cruise afternoon tea tours and plainer River Thames sightseeing cruises share the same channel each afternoon. The boats are built for the constraints of the river. Hulls carry low superstructures and glazed roofs so they clear the arches of Westminster, Blackfriars and Southwark bridges at high water, and shallow draughts suit a channel that silts and scours with every tide. Galleys are compact, which is why the menu follows the traditional order: finger sandwiches, then scones with clotted cream and preserve, then pastries, with Earl Grey poured against the motion of the deck. Departures leave from Tower Millennium Pier on Lower Thames Street, within sight of the Tower's wharf. Seven days a week, the London afternoon tea cruise keeps to the same hour, and a Thames cruise afternoon tea remains one of the few rituals in the city that is measured in tides rather than minutes.