London’s most iconic landmark is giving up its secrets when Tower Bridge throws the doors open for the public to peek behind the scenes.

The bridge keepers are running engineering tours in the New Year where the curious can see how the huge machinery lifts the bascule bridge to let ships into the Pool of London.

The inner workings of the world’s most famous river crossing will be open every weekend in January and again in March.

But it’s not cheap. Tickets for the two-hour tour are £29 to see all the areas normally off limits to the public.

The tour begins with the permanent exhibition in the original high-level pedestrian walkway 130ft above the Thames, with its panoramic view of the London skyline, showing the history of Tower Bridge as the marvel of the Victorian Age.

It continues to the atmospheric setting of the original 1894 engine rooms with their restored steam pumps, accumulators and boilers that were used to power the lifting bridge until 1976.

The tour also takes in the bridge control room, the huge bascule chambers below river level and the machinery room housing the massive hydraulics powering the lifting gear.

Tours start from 4pm, each limited to 12 places. But individual tickets are also available for those who don’t want to join a group. Booking by phone is 020-7407 9191, or email enquiries@towerbridge.org.uk.