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The Royal Marines skied 1,664km from Porsangermoen, in northern Norway, down to the southern port city of Stavanger.
They completed the distance in just under 2 months with conditions ranging from blizzards to bright sunshine and temperatures of between -20°C and +10°C.
But now they have arrived in Stavanger there is little time to rest as they get straight into the next phase, a 1,664-nautical-mile sail from Norway down to Cadiz, in Spain.
Captain Sam Moreton, one of the Royal Marines taking part in the challenge, said:
When we set out at the beginning of February, Stavanger seemed a long way away, especially when we considered the arduous conditions that lay ahead across some of the most inhospitable terrain in Europe.
But we gelled into a formidable unit with a fantastic team spirit and have been working very well together in true Royal Marine fashion.
Royal Marines 1664 Challenge
The Royal Marines Corps was formed in 1664, and this year marks its 350th anniversary. To commemorate the historic occasion, a challenge was devised that would test Royal Marines both physically, and mentally, and display the true commando spirit and determination to succeed.
The Royal Marines 1664 Challenge was the result; an event that covers roughly 4,136 miles (6,656km) by ski, sail, cycle, canoe and then by foot.
By the time the 1664 Challenge concludes, with a marathon around London in July, more than 4,200 commandos will have taken part.
Getting the 1664 Challenge underway were 19 commandos who set out on skis from Porsangermoen at the beginning of February, with 6 of them expected to take part in the challenge right through to London.