A FRIEND of a Caldicot man who is missing with what is believed to be a rifle said he sounded depressed during a telephone conversation a week ago.

Concern is growing for the safety of 64-year-old retired steelworker Derek John Upton, who has been missing from his home since Sunday morning.

Bob Trett, who has known him for 20 years, said his friend had an industrial accident about 15 years ago.

"He had to give up work because of the accident and has a lot of trouble with his legs," said Mr Trett, of Goldcroft Common, Caerleon. "He's on a high dosage of painkillers and he was very depressed about that."

Mr Trett, former curator of Newport Museum, said Mr Upton has made many important archaeological discoveries in the Severn Estuary, including some of the earliest footprints ever found.

"Everybody goes to Derek because he understands the estuary," he said. "But in recent years, because of his legs he hasn't been able to get into the estuary in the way he would like.

"He knows the estuary like the back of his hand and his car was found nearby. I'm just very concerned about him."

Because of his archaeological work, Mr Upton received an honorary degree from the University of Wales. He is also a voluntary warden at Magor Marsh, where there is a learning centre named after him.

Police say Mr Upton, who is a member of a rifle club in Rogiet, is not a danger to the public but are urging people not to approach him. They said there are concerns for Mr Upton's welfare as he has been extremely depressed over the last few days.

The last sighting of him was at the Moors at Rogiet. His car was recovered on Monday from the mud flats nearby. Mr Upton, who is married, was last seen wearing striped shorts and a T-shirt. If anyone has information they are asked to call Gwent Police on 01633 838111.