麻豆社

The Thames Barrier was officially opened 40 years ago by Queen Elizabeth II on 8 May 1984. It was designed to protect London from flooding until 2030, and is now expected to function until 2070.

Without the barrier, which is downstream from Greenwich and close to City Airport, officials said storm surges and frequent tidal flooding of the Thames would submerge buildings along the river, risking lives and livelihoods and causing huge amounts of damage.

It has been closed 221 times to prevent flooding in the capital.

To mark it's 40th birthday, 麻豆社 Radio London's Salma El-Wardany has been finding out how it all works.

(Image credit: Getty Images)