Ollie Peart finds out what St Paul's Cathedral, The Cenotaph and the United Nations Building in New York have in common with Portland Stone, which is mined from the Isle of Portland quarries in Dorset.

The 150-million-year-old stone bears the fossilised imprint of creatures from the Jurassic era. The mining process has left behind a colossal, cavernous space. Huge, vaulted ceilings bridge between vast pillars of Portland Stone left by the miners. The miles of tunnels which twist and turn, hidden from the residents of Portland, could also hold the key to their future.

There's a proposal to turn these deep mines into a biodiversity attraction where visitors can marvel, explore and learn about the future of this unique place and how it connects with the rest of the planet.

Hosted and produced by Ollie Peart and Ian Ramsdale.

Online producer: Rachael Smith.

Executive producer Kathryn Morrison.

Thanks to Mark Godden (Mine Manager, Albion Stone) and Sebastian Brooke (Project Director).

Archive of Churchill and Cenotaph: www.bbc.com/historyofthebbc/buildings/broadcasting-house

Featuring an extract from Greta Thunberg’s speech at the UN, 2019.