The Duke of Cambridge has sent a Christmas message to an explorer trekking to the South Pole, and told him "you are doing a cracking job".
Former Army officer Henry Worsley, 55, is attempting to become the first solo adventurer to cross the Antarctic unassisted and unsupported.
He is enduring freezing temperatures, high winds and treacherous ice as he treks to the South Pole and then travels to the other side of the land mass.
William, who is patron of Mr Worsley's 2015/16 Shackleton Solo Challenge, took time out from his family Christmas to send the intrepid explorer a festive message.
The Duke said: "Henry, it is Prince William. I just wanted to wish you well and to say that we are thinking of you over the Christmas period as you are lugging all your kit up and down the slopes and the hills of the southern Atlantic and the Antarctic."
William went on: "Good luck for the rest of the expedition, I know you are planning hopefully to reach the South Pole by New Year, so that will be a good New Year's Eve Celebration.
"You are doing a cracking job. Everyone back here is keeping an eye on what you are up to, and are very proud of everything are achieving.
"Particularly the fact that you are doing this for the Endeavour Fund is extremely impressive, for all the sick, wounded and injured veterans, so I hope that keeps you motivated, I am sure, for the next few weeks.
"We are all thinking of you and good luck for the rest of the trip. I hope you keep warm and it's not too painful down there."
Mr Worsley, a former lieutenant colonel, is hoping to raise £100,000 for the Endeavour Fund, a body established by the Royal Foundation of the Duke and Duchess of Cambridge and Prince Harry to fund sporting and adventure challenges aiding the recovery of wounded, injured and sick servicemen and women.
He has set out to complete Sir Ernest Shackleton's unfinished journey to the South Pole from the Weddell Sea following part of his intended route.
He is on skis and pulling a sledge containing his food, tent and other equipment, but unlike previous Antarctic expeditions by other explorers, he will not receive supply drops or help across the ice from dogs.