Deep down the streets of London there is a secret underground vault where 4,600 tons of gold of the Bank of England is stored.All this £197 billion worth of gold bullion is carefully guarded and rarely seen by outsiders.

Each shelf in the warehouse holds £35 million worth of gold.

Chemistry professor Martyn Poliakoff of the University of Nottingham has just been allowed to visit the British treasure.

In this warehouse, about 310 tons of gold are deposited by other organizations and countries. Each gold bar is printed with a serial number and year of manufacture. The oldest gold bar here is dated 1916.

Even when sold, the gold in this vault is not taken out, but simply converted to the owner’s name.

If you consider all this gold as a brick, using them can build a wall 20m high, or a square wall measuring 18mx18m.