Thunberg, who became a prominent campaigner worldwide after staging weekly protests in front of the Swedish parliament in 2018, was acquitted at Westminster Magistrates’ Court of a single charge under the Public Order Act.

Thunberg was one of dozens of people arrested in October outside a London hotel where the Energy Intelligence Forum was hosting oil and gas industry leaders.

She and four others, aged between 19 and 59, were accused of failing to comply with an order by police to move their protest to a designated area near the conference.

But Judge John Law ruled that the condition placed on the protest was unlawful because police could have imposed lesser restrictions and because the conditions were not clear.

“The prosecution evidence is insufficient for any reasonable court to properly convict and I exercise my discretion to acquit all five defendants,” Law said, to applause and cheers from a packed public gallery.

Addressing the five defendants, he added, “You are all found not guilty of this offence.”

Thunberg and her four co-defendants hugged before leaving court.