All six of the Britons arrested by Russia during Greenpeace protests in September have now been freed, with five of them returning to London.
The six Britons were among 30 people detained in September during demonstrations at sea against oil drilling in the Arctic by Russian energy giant Gazprom.
The group, dubbed the 'Arctic 30' by Greenpeace, were charged with piracy by Russian authorities, an approach deemed heavy-handed by Prime Minister David Cameron and other European leaders.
One of the freed Brits, Anthony Perrett, 32, said his ordeal "was definitely worth it" and that he would return to the country if needed.
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"It's been a very long 100 days," he said before leaving Russia. "I'm quite eager to get back to Wales and sleep in my own bed and get back to work."
Alexandra Harris, Anthony Perrett, Phil Ball, Kieron Bryan and Iain Rogers left St Petersburg and travelled from Paris by Eurostar to meet their families in London. A sixth Briton, activist Frank Hewetson, has also been released and is travelling to another country.
Members of the Arctic 30 were released on bail in November and all charges against them were dropped on Boxing Day, although some - including one of the released British activists, Alexandra Harris - believe the move was designed to improve Russia's image before the Winter Olympics begin in Sochi in February.
Ms Harris told ITV News that she and other members of the Arctic 30 were "treated better than the Russian prisoners, because the world's watching us".
"We spent two months inside a Russian jail cell and a hundred days detained for a crime we didn't commit," she added. "It was obscene, a complete overreaction on behalf of Russia and we should never have been there."