Tickets Alert: Behind the scenes tours of Tower Bridge

"Deep under Tower Bridge lies a vast space that almost seems larger than it can be, and during the winter months, the public can go inside for a look. This is one of Tower Bridge's two bascule chambers and is basically where the heavy counterweight swings into when the bridge opens to let boats pass through. But not when you're standing in it - and that's why tours take place during the winter, when fewer boats ply the Thames."

"Firstly, into one of two control cabins. While one is modern and controls everything, this one has been retained in its original Victorian design and was in use right up to the 1970s. And yes, those are railway signal levers used to control the mechanism, and yes, there is a proper railway signalling interlock mechanism underneath, although you don't get to see that bit. What you do see, though, is the basement where the modern engines sit next to their Victorian predecessors."

Two-hour behind-the-scenes tours run most weekends from November through March and include areas seen on the normal public route plus an off-limits bascule chamber. Tours visit one of two control cabins, including an original Victorian cabin with railway signal levers and a signalling interlock mechanism, as well as the basement where modern engines sit beside Victorian predecessors. The route passes old hydraulic accumulators, a narrow underground corridor, and the vast bascule chamber below river level. Tours finish in the old steam engine rooms. Tickets cost approximately £80 adults, £72.50 children, with a disabled adult rate.

Read at ianVisits