Oscar-winning actress Dame Emma Thompson who said she wants to be arrested at the Extinction Rebellion protests, stood on top of a pink boat that has blocked traffic from Oxford Circus for five days as she rallied demonstrators in London.

The Hollywood actress, who flew 5400 miles into London Heathrow from Los Angeles on Wednesday, laughed with demonstrators in the capital as youth members of the group held a so-called Day of Love.

Many protesters have previously called for the government to limit how many times individuals can fly a year, with ringleader Robin Boardman-Pattison even declaring that planes should be ‘only used in emergencies’.

A flight from LA to London Heathrow is estimated to generate around 1.67 tonnes of CO2.

Following an increased police presence, for Ms Thompson's speech, officers were not letting people into the circle around the protesters.

Ms Thompson climbed a ladder to the deck of the pink boat to cheers from the crowd, before dozens of police officers strode into the crowd of activists and surrounded it.

She said that she had come to support the movement and had been greatly inspired by it, adding that her generation and politicians had failed young people.

The 60-year-old movie star said: "We have seriously failed them and our planet is in serious trouble, we have much, much less time than we thought.

"I have seen the evidence for myself and I really care about my children and grandchildren enough to want to be here today to stand with the next generation.'

The actress added: "This is the most pressing and urgent problem of our time, in the history of the human race.'

When asked whether protesters were having too much fun, she said they should have a sense of joy adding: "If you can't have fun whilst saving the planet, what's the point?

"Protest should always have a sense of joy in it because what we are protesting about is saving this extraordinary home of ours and also celebrating the passion and inspiring energy of this young generation.

"These are young people who have finally said to my generation, 'I'm so sorry but you have failed us'. We all feel dreadful about that. My feeling is I feel massively inspired by this young generation and want to stand next to them."

She added: "We are here in this little island of sanity and it makes me so happy to be able to join you all and to add my voice to the young people here who have inspired a whole new movement."

Dame Emma, who has been urging more people to join the climate change movement, is expected to be joined by actors Lee Ross, from White Gold and The Catherine Tate Show, and Paapa Essiedu, from Press and Kiri.