A father has issued an emotional appeal for help in the search for his son who is thought to have gone missing while hiking in Canada.
Tom Billings, 22, described as a seasoned traveller and avid hiker, was reported missing after he failed to return to accommodation in Vancouver for several days.
The recently-graduated student, who was exploring North America for the first time, has been missing since November 25, Canadian police said.
A number of tips have led them to believe he went to the North Shore area of Vancouver on a hiking expedition.
His father Martin Billings, a lawyer from Oxford, speaking at a police press conference in Vancouver, issued an appeal for information to help trace his son.
He said Tom, who had no medical problems, graduated recently from university and had applied to carry out postgraduate research.
He had been using a "window" of eight to 10 weeks to explore North America hitch-hiking, travelling by bus and using "couch surfing" - staying with hosts he had met through the internet - as accommodation.
Mr Billings said he last exchanged emails on November 22/23 when his son was in Seattle in the US. He said Tom was in a "light-hearted" mood.
He said it is believed that Tom headed for a hike and he left his backpack and laptop computer at the house where he was staying.
"He left his backpack at the house and police think it is fairly clear that he wasn't intending to stay out anywhere for an immense amount of time. We think he would have got himself up to the North Shore and gone out for a three to four-hour hike," he said.
"We think that Tom could be out there somewhere. Hopefully, he's holed up in a warm place and someone has seen him who can pass information on to police," Mr Billings said.
"I think the most likely thing is he has got in trouble on the mountain.
"We just hope he can be found somewhere safe and can get back to his normal life."
He said his son would probably have intended to stay in Vancouver for "one or two" more days before making his way east to catch a flight from New York City on December 7.
Asked at the press conference what his "gut instinct" was about what happened to his son, Mr Billings said: "The things that have gone through my mind are in many ways too horrible to mention, I cannot deny that.
"I think most likely is that he got into trouble somewhere on the mountain. From there, I do not know. What I hope is that he got to a warm place - maybe he has broken a leg or something."
Rescue teams have conducted a "massive sweep" of the area Tom is thought to have visited and are now preparing to conduct another search of a wider area, he said.
The backpacker discussed a number of locations he wanted to visit in the Lower Mainland, including the North Shore mountains. He had been due to return to England last weekend.
A Vancouver police spokesman said "no tip was too small" in helping to trace Tom.
"Tom Billings is a very experienced hiker, as you can tell from what his father tells us. Our concern is that he is injured and he is out there and needs help," he said.