Video footage of the stunt - they had invited some media - went viral online. One clip proving particularly popular was set to the Benny Hill theme tune, Yakety Sax.

Eight people, including an 83-year-old grandfather of four, were arrested on suspicion of criminal damage.

Campaigners insisted they wanted to highlight the inconsistency between the Government claiming to be a world leader in tackling climate change and its funding of fossil fuel exploration.

A banner unfurled on the decommissioned fire appliance read: “Stop funding climate death”.

An Extinction Rebellion spokesman said: “It is time to imagine a future where humans no longer cause irreparable harm to themselves and their surroundings, but recognise and support the interconnectedness of life in its broadest sense.”

The protest was meant to be an “opener” for next week's International Rebellion, when more than 20,000 Extinction Rebellion activists are reportedly threatening to paralyse central London.

They plan to converge on Lambeth and Westminster bridges, London City Airport, Smithfield meat market and Trafalgar Square.

Activists could also try to prevent the Queen's Speech from taking place on October 14, The Times said.

In London, Scotland Yard has warned that it is under more pressure from Extinction Rebellion protests than they faced during the terror attacks of 2017.

Around, 30 police officers surrounded the fire engine outside the Treasury before it was eventually “seized and removed”.

Following the protest, a Treasury spokesman insisted the UK was a “world leader on climate change”, having reduced its emissions by 42 per cent between 1990 and 2017, while growing the economy by more than two-thirds.

Penny Mordaunt, the Tory MP and former Defence Secretary, took to Twitter: “I know they didn’t mean it to end this way, but this was a dangerous stunt. Out of control hoses under pressure can do serious injury. The public should never be put at risk from such protests.”

Fake blood protest, in pictures