The wife of a British explorer who has gone missing on an expedition to reach a remote tribe in Papua New Guinea said their three children are "seriously worried".
Benedict Allen was dropped by helicopter into the remote jungle three weeks ago and has not been heard of since.
He was hoping to reach the Yaifo, a tribe thought to be one of the last on Earth to have no contact with the outside world.
His wife Lenka Allen told the Daily Mail their children - 10-year-old Natalya, Freddie, seven, and two-year-old Beatrice - keep on asking "when's Daddy coming home?"
Mrs Allen told the newspaper: "The little one, Beatrice, is always saying 'Daddy' and she's trying to telephone him on my mobile, looking at his photo on the screen.
"They all sense the tension in the flat and they are worried deep down.
"The two other ones, they are saying, 'When is Daddy coming so we can go shopping, just me and you, and Daddy can babysit', that sort of thing. But of course now they know he's in danger, they are seriously worried."
She added that "everything possible" is going through her head, fearing he had been bitten by a snake, got lost or contracted an illness - but added: "He does know a lot about the jungle."
The author and TV presenter, who has made six TV series for the BBC, has no mobile phone or GPS device with him and was expected to begin his journey home at the weekend - but failed to make a flight to Hong Kong.
In a blog post on his website, Mr Allen wrote in September: "The Yaifo are one of the last people on the entire planet who are out of contact with our interconnected world.
"In October I'm hiring a helicopter to drop me off at the abandoned mission station, Bisorio - a forlorn place.
"Last time the Yaifo greeted me with a terrifying show of strength, an energetic dance featuring their bows and arrows.
"On this occasion who knows if the Yaifo will do the same, or run off, or be wearing jeans and T-shirts traded eons ago from the old mission station.
"Nor do I have an obvious means of returning to the outside world, which is somewhat worrying, especially at my advanced age.
"Either I must paddle down river for a week or so - or enlist the help of the Yaifo, as I did last time.
"So, if this website or my Twitter account falls more than usually silent - I'm due back mid-Nov - it's because I am still out there somewhere.
"So, don't bother to call or text. Just like the good old days, I won't be taking a sat phone, GPS or companion. Or anything else much. Because this is how I do my journeys of exploration. I grow older but no wiser, it seems."
A Foreign and Commonwealth Office spokesman said: "Our staff are assisting the family of a British man who has been reported missing in Papua New Guinea, and are contacting the local authorities."