Pen Hadow's phone has gone dead
Fears are growing for the safety of Arctic explorer Pen Hadow who has been stranded on drifting ice for five days.
Bad weather has forced rescuers to abandon their latest attempt to reach him by plane.
And his wife has told the BBC Mr Hadow is physically exhausted and completely cut off from contact with the outside world.
Mary Hadow's comments came as she received a telegram from the Queen, congratulating her husband on his "courage, perseverance and determination" on his "remarkable" journey.
"You have defied great odds and extreme conditions in your endeavour," the Queen said.
"I offer you my warm congratulations."
Mrs Hadow said the 41-year-old was so tired that his legs kept buckling and he could not stand up properly.
On Monday, Mr Hadow became the first person to travel solo and unsupported from northern Canada to the geographic North Pole - starting at Ward Hunt Island.
Mrs Hadow said the last time she had spoken to her husband he had been "very tired, but very cheerful".
I think because he is all alone and so tired, Pen will be having a really
But she added: "My concern is that when the adrenaline disappears then he might start feeling ill."
Mr Hadow's satellite phone batteries have stopped working, leaving his rescue team unable to tell him what is happening.
His signal beacon is sending out a message saying "non-urgent pick up requested here. Conditions OK for plane to land".
He is known to have prepared a landing strip.
Planes sent to pick him up on Thursday were forced to turn back because of bad weather and it has not been possible to tell him why they did not arrive - or when he can now expect to leave the ice.
"What I'm concerned about is that he lives for communication - he just loves other people," Mrs Hadow said.
"So not being able to talk to anybody, for him, will be terrible."
The explorer only has snack food, including dried fruit, nuts and chocolate to keep him going and if there has been no rescue by Wednesday, it is hoped rations can be dropped on to the ice.
Mrs Hadow, who lives with her husband and their two children in Dartmoor, Devon, said: "I think because he is all alone and so tired, Pen will be having a really
She said she was not unduly worried about his safety, although there was a small chance that polar bears could be near his camp, or that the ice could crack under his tent.
Mrs Hadow said: "The telegram was nice. I know the Queen is interested in arctic issues.
"What I think is quite extraordinary is how people have taken Pen, and his approach to life, to their hearts.
I always knew he was exceptional and it seems the whole world knows it too
"To some people he has come an icon for spiritual inspiration. He was even mentioned on (Radio 4's) Thought for the Day last week."
"I always knew he was exceptional
and it seems the whole world knows it too."
Mr Hadow, from Dartmoor, in Devon, has had no human contact since 17 March, and last spoke to his wife on Monday to say he had reached his goal.
The explorer braved freezing temperatures, swam in the freezing sea, and negotiated huge pressure ridges during his 478-mile solo trek.
The aircraft is due to take off, when weather permits, from Eureka weather station on Ellesmere Island.