All aboard for a brothel, mass murder and mud

Guided tours don't often come like those aboard the capital's Docklands Light Railway. My guide was a "passenger service agent" called Amelia, and in between telling me about death and prostitution, she has to be ready to take the helm of this driverless 1980s contraption, should the computer fail.

Nor is the trip – from just east of the Tower of London to the Greenwich World Heritage Site via a cityscape of historical gore and capitalist bravado – like your average scuttle around a stately home.

I'd already got value for money by the time the train trundled into Shadwell station. Amelia, a bob-haired cynic with a taste for the macabre, recounted the story of John "the throat-slitter" Williams. The servant girl of a Mr Marr was sent out for oysters in 1811, apparently, only to return to find her employer, his wife, their baby and a shop boy butchered. Williams was to strike again before the law caught up with him, at which point he avoided the gallows by hanging himself. His body was paraded before a baying crowd and, said Amelia gleefully, "a stake was driven through his heart".

From Shadwell, we charted a thin line between soulless post-Blitz council schemes, Hawksmoor churches and new Thames-side marinas, before the train arched up and south over West India Docks into the shadows cast by the multiplying skyscrapers of Canary Wharf. Amid the glass-and-steel façades, it is easy to forget this was once London's dirty trading hub. Amelia will tell you of walled, guarded docks packed to bursting point with the pickings of an empire and of waters so poisonous that overworked dockers would throw themselves in for the sake of the day off.

On past the huge building site, we reached the heart of the Isle of Dogs (where Henry VIII kept his dogs). Here is The George public house, a former dockers' brothel, and Mudchute, a massive mound of silt scooped out during the construction of Millwall dock. Under the Thames and it was soon time to bid farewell to Amelia who was yelling: "All aboard for sunny Lewisham before I get shot!" as we disembarked.

Emerging from Cutty Sark station to the sight of the glorious tea-clipper herself, I felt an overwhelming sense that I had stepped back into an age of king's shillings, sea trade and ship rigging. Breathe in and you might catch the scent of the sea.

Free guided tours run seven days a week on some trains. Docklands Light Railway (020 7363 9700).