Dr Stevens may have been seen on a train to London

Dr Stevens, 54, arrived for work at the Royal Manchester Children's Hospital in Pendlebury, Salford, last Monday.

He left his jacket and briefcase in his office, and has not been seen since.

Dr Stevens' son Jonathan, 30, said his father's disappearance was totally out of character and said the last week had been his "worst nightmare".

Greater Manchester Police are investigating an unconfirmed sighting of Dr Stevens on a train to London on Tuesday - the day after he went missing.

CCTV footage is being examined to see whether he was among the passengers on the 1227 BST train from Manchester Piccadilly to Euston.

Family pleas

Just days before Dr Stevens disappeared he had celebrated the graduation of his elder daughter, Helen, at Manchester Metropolitan University.

The 27-year-old said: "He was really chuffed for me.

For whatever reason, he has gone away but we believe deep down as a family that he is all right Jonathan Stevens

On Monday, his three children, Jonathan, Helen and Rebecca pleaded with him to let somebody know he was safe.

Jonathan, 30, said: "You never expect anything to happen like this to yourselves, especially Dad who was such a normal guy, such a level-headed, straightforward thinking individual."

Jonathan said there had been nothing of any note in the days before his father's disappearance to give the family any suggestion as to why he might have left.

Younger daughter Rebecca, 19, said her parents had had a tiff but that by Sunday evening everything was back to normal.

Jonathan said: "We believe he is out there and he is all right.

"For whatever reason, he has gone away but we believe deep down as a family that he is all right.

"For some reason there is no contact but all we ask is that he makes a call, it does not have to be to us personally, but just make a call to say you are OK."

Superintendent Frank Doyle, of Greater Manchester Police, said officers were sifting through a large number of possible sightings they had received over the past week.

He said: "It appears that he may have taken it upon himself to go away. We are not in any fear for his safety.

"The family are very distressed, as are a lot of his colleagues. We have to ensure he is safe and well."