The stunt, at a busy junction in Covent Garden, threatened to cause delays to ambulances, fire engines and police cars in emergencies. Drivers were left fuming as traffic jams built up, while protesters set off flares.
Eight people were arrested. Some protesters set up tents in the street while others locked themselves to the legs of the 13ft table.
Yesterday’s protests got under way with a marching band in Trafalgar Square.
It was the start of a planned two weeks of disruption by XR activists, who want an end to government investment in fossil fuels.
It followed a “warm-up” demo at London’s Guildhall on Sunday with nine arrests.
A series of protests in 2019 and last year left taxpayers with a bill for more than £50million in policing costs.
That will now soar as thousands are expected to join in over the next fortnight.
Gail Bradbrook, co-founder of the group, opened what she called the Impossible Rebellion with a speech expressing solidarity with nations that are disproportionately affected by climate change.
Some activists planned to stay for a long time and even chained themselves together, or to vehicles.
Police promised a “significant” operation to tackle the protests, particularly over the bank holiday.
Britain will host the COP26 summit in November to discuss global warming.