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t’s the most spectacular – and unusual– light show on Earth. At 8.30pm on Saturday, hundreds of British landmarks, from Buckingham Palace to Edinburgh Castle, will be plunged into darkness for the tenth anniversary of Earth Hour.

They’ll be joined by millions of homes, businesses and schools in more than 170 countries who will turn their lights off for 60 minutes in support of tackling climate change.

In total, more than six million people in the UK are expected to turn off their lights, with Leeds Town Hall among more than 12,000 landmarks and national monuments worldwide signing up to take part in the environmental extravaganza. Earth Hour started in Australia in 2007, with Britain joining in the following year. In 2016, over six million people in the UK took part. Supported by players of People’s Postcode Lottery, this year’s Earth Hour, organised by WWF, is set to be the biggest yet.

The Gherkin, London Eye and the OXO Tower will join in. Arsenal will switch off the lights at The Emirates Stadium, along with Brighton Pier, Aintree Racecourse, Windsor Castle, Clifton Suspension Bridge and Liverpool’s Radio City Tower.