Five British members of the 'Arctic 30' return to Britain and vow to continue the campaign

Greenpeace campaigners were greeted by jubilant friends and family at St Pancras Station on Friday night

Freelance videographer Kieron Bryan (second left) with Greenpeace activists, Anthony Perrett (left), Alexandra Harris, Iain Rogers and Phil Ball (right), as they arrive at St Pancras Station, London, after being detained in Russia as part of the so-called (Jonathan Brady/PA)

Families of the Arctic 30 received a belated Christmas gift on Friday night as five of the British contingent that formed part of the Greenpeace campaign group finally came home.

Greeted by friends and family at London's St Pancras International, the quintet - activists Phillip Ball, Alexandra Harris, Anthony Perrett, Iain Rogers and freelance journalist Kieron Bryan - returned to Britain with a defiant message.

"Our campaign continues, it is part of my heart now," said Ms Harris. "We will carry on."

They were arrested in September when Russian authorities boarded their ship, the Arctic Sunrise, during a protest against an offshore oil rig owned by the Russian company Gazprom. The group of 28 activists and two freelance journalists were held on piracy and hooliganism charges and faced up to seven years in jail but after two months in prison, and five weeks on bail staying in a St Petersburg hotel, were released under a new Russian amnesty law that has also seen members of punk band Pussy Riot and former oil tycoon Mikhail Khodorkovsky.

A sixth Briton, Frank Hewetson, was travelling to another country, according to Greenpeace. Canadian Alexandre Paul was also expected to arrive in Montreal later on Friday.

Labour's deputy leader Harriet Harman said the group's homecoming before New Year was "terrific news".

Speaking after their arrival on Eurostar from Paris, Mr Ball was scathing about the prison conditions they endured.

He said: "It was squalid, depressing and hideous. The cell which we were kept in for 23 hours a day was eat and fly infested. The state of the Russian penal system is an absolute embarrassment to Russia."

Ms Harris also said the food was "inedible". Both said the stress was worth it.

Mr Bryan, who wrote a letter to his parents detailing he was mentally preparing for a lengthy sentence, said: "I wrote that letter because a genuinely feared for my chances of becoming a father.

"The whole process was a political game but it's vital that the discussion (about oil drilling) continues. In Russia there is only one man who can change things and the issue everyone campaigned for needs to be kept alive."