A doctor who disappeared almost four weeks ago from the hospital where he worked has been spotted wandering through an airport in a "confused and disoriented" state.

Police said there had been a confirmed sighting of Dr Richard Stevens, a consultant haematologist, at Liverpool's John Lennon airport in the early hours of Thursday.

Closed-circuit television pictures showed Dr Stevens, 54, who has three children, sitting with a black bag on a bench, staring forlornly into the distance. One of the lenses in his glasses was broken. He told a member of staff he was heading north, and took a cab to Lime Street train station, after which he went missing again.

Dr Stevens' family is convinced the man seen on the CCTV footage at the airport is the doctor. The sighting is the first firm news they have had since he disappeared from the Royal Manchester Children's Hospital in Pendlebury last month. There was no indication he was about to go missing.

Monday, 21 July started as an ordinary day. Dr Stevens set his alarm for 6.38am, as usual, kissed his wife, Eirwen, and left his home in Sale, Greater Manchester, at 6.50am. Shortly after 7.10am he arrived at the hospital, parked his car, and walked through the main entrance to his office where he left his jacket and briefcase.

Then, nothing. His Audi remained in the car park. CCTV cameras did not record him leaving the building. Police searches of the 19th-century hospital found no trace of him. His mobile phone was switched off and he has made no contact with his family since. His passport was still at home. No money has been withdrawn from his bank accounts.

Dr Stevens was highly respected at the hospital, work-ing with children suffering from leukaemia and haemophilia. Professor Tim Eden, his closest colleague, described him as "one of the most personable people you could meet".

At home, Dr Stevens appeared to have a settled life. He had been married for 31 years, with three children - two daughters, Rebecca, 19, and Helen, 27, and a son, Jonathan, 30. He adored classical music and played the cornet in a brass band. He had rebuilt an old Panther car.

Mrs Stevens said her husband was a man of routine, and described his disappearance as "totally out of character".

Yet there may have been discord in Dr Stevens' mind - he had a family argument the day before he disappeared. His work with sick children, which he found difficult to talk about with his wife, may, finally, have got to him.

Members of the public have come forward with sightingsof the doctor. He was thought wrongly to have boarded a London-bound train, and a woman reported this week that she believed she had given him a lift in Devon. But until now no sighting has been confirmed.

The breakthrough came when a confused man in his fifties spoke to an employee at Liverpool airport. He was wearing cracked spectacles, a beige coat, with black trousers and black shoes. Immediately afterwards he took a taxi to Bolton Street in Liverpool, close to Lime Street station.

A spokeswoman for Greater Manchester Police said Dr Stevens' family had seen the airport footage and were convinced the man was Dr Stevens. Sergeant Julie Connor said: "The man in the footage appears confused and disoriented and we are concerned that Richard may have suffered some sort of breakdown and does not know where he lives.

"These images suggest that he is so confused he may not know who he is or that he has a family that love him and want him home.

"We would really like to hear from any rail passengers who travelled through [Lime Street] station [on Thursday] morning and can help us establish where Richard went from there.

"We would also like to hear from any rail passenger who travelled through the station [on Thursday] morning and saw a man fitting Richard's description. Perhaps he got on to your train."

Dr Stevens, or anyone who knows of his whereabouts is asked to contact police at Salford on 0161-856 5143.