Welcome to the fourth and final of our special London Microguides. This week, following on from our guides to Wild, Cheap and Eat London, we turn our attention to the secrets that this great city conceals.

We hope you agree that we’ve uncovered some great tales and intriguing sights, but if your favourite is missing, please tell us in an e-mail to: secretlondon@thetimes.co.uk.

With satellite navigation and mobile internet in mind, we have included full postcodes where possible.

THE HIDDEN CITY, BEFORE YOUR VERY EYES

London is a city that sits on its ancient forebears. But not all its secrets are buried. Everyday sights also have their stories.

Take the shape of the humble bollards on India Street, EC3, one of few locations where original Georgian examples remain. Why are they that shape? They’re made from disused cannons, with cannonballs blocking the muzzle. Look down to Tower Bridge, a landmark that’s not as old as it looks (1894), and is made of steel with stone cladding. Beneath the water level are huge chambers for the bascules’ 1,000-ton counterweights, which swing down whenever it is opened.

Head west to Cleopatra’s Needle for more history staring you in the face. Buried in sand for 2,000 years, it was presented to Britain in 1819 by the viceroy of Egypt, then took a further 58 years to get here. On a stormy crossing, it was nearly lost, and erected in 1878, with a Victorian time capsule in the plinth. In 1917, it became the first monument damaged by World War One bombs, whose marks are still visible.

The Tube and electrification also changed the city in ways we barely think about. Piccadilly Circus is London’s only neon hotspot because leases on its buildings prohibited signage on the rooftops, but not the walls. Soho to the north was soon a big user of electricity, requiring its own substation. Where better to conceal it than inside a mock Tudor garden shed, slap-bang in the centre of Soho Square (above)? But if there were a prize for concealment, it would surely go to 22-23 Leinster Terrace W2, whose imposing “buildings” are merely 18-inch thick screens, shaped like houses and constructed to hide the tube line behind.