Experts have begun to repair the moat wall

A stretch of stone dating back to the 19th Century crumbled away last month.

Building work is being carried out to improve access to the Tower, one of London's most famous buildings, built after the Norman Conquest in the 11th Century.

But a spokeswoman for the Historic Royal Palaces, which is responsible for the Tower's conservation, said it was not related to the collapse on 14 February.

She said: "This work is entirely unconnected with the work currently taking place on Tower Hill, which will improve the accessibility and appearance of the area to create a pedestrianised, safe, civic space for London."

Experts have begun taking down part of the wall, removing stones and railings, in order to repair the damage.

The collapse exposed stonework from an earlier period which is being studied and is described as "archaeological evidence of great interest."

The wall in question had been under observation for some time and work was due to be carried out on it in the near future.

Archaeologists, conservation specialists and English Heritage are involved in the stabilisation, repair and long-term monitoring of the moat wall.