The father of a gifted teenager from South Yorkshire has appealed to his son to get in touch, a month after he travelled to London and disappeared.
Andrew Gosden, 14, went missing on 14 September after failing to turn up at school in Doncaster.
He took £200 from his bank account and was spotted heading to London on a train. Police have now released CCTV footage of him at Kings Cross station.
Andrew's father Kevin said: "Please let us know you are OK."
There have been various sightings of the pupil in areas of the capital, but he has failed to get in contact with family or friends.
Mr Gosden, 41, a speech and language therapist from Balby in Doncaster, said he had made various trips to London in a bid to find him.
He said: "I spent last weekend in London distributing leaflets and visiting places where he might be.
"A lot of my family live in London. It's familiar to him. It's a big exciting place."
Mr Gosden said his son seemed happy with his life with no obvious problems.
In a message to his son he said: "Please get in touch. We love you, we care about you desperately. Please let us know you are OK".
Andrew's mother, Glenys, 43, and sister, Charlotte, 16, have also been looking for him in London.
Andrew, who is 5ft 3in, of slim build with straight brown hair, is believed to be wearing a black top, black jeans, trainers and was carrying a black bag with patches of rock bands on.
CCTV footage shows him arriving at Kings Cross station at 1120 BST on 14 September.
Police officers from Doncaster are in London, where they are working with the Metropolitan Police and British Transport Police to find him.