A retired entrepreneur has vanished after being dropped off at the seafront home of a mysterious acquaintance.

A major police investigation has been launched into the disappearance of Roy Chalmers, 79, who went missing on Easter Monday.

Officers said they were becoming increasingly certain Mr Chalmers had been the victim of a serious crime.

The pensioner, from Patcham, Brighton, is frail with a heart condition and unable to walk far unaided.

He was last seen at 6.50pm on Monday when he was dropped at Marine Gate flats, near Brighton Marina, by a friend visiting from London.

Detective Chief Inspector Steve Dennis, who headed the successful hunt for the killer of Brighton teacher Jane Longhurst a year ago, is leading the investigation.

He said: "This is now a major inquiry. We are carrying out similar inquiries as we did when Jane disappeared.

"We are checking with banks to see if any transactions have been made and studying phone records."

The alarm was raised by the friend from London, who has not been publicly identified. He told police he had been caring for Mr Chalmers and drove him to the flats on Monday evening before returning home.

He tried to contact Mr Chalmers the next day and called police when he was unable to do so.

The friend did not know who Mr Chalmers was visiting. Police checks with Marine Gate residents have so far proved fruitless.

The disappearance was said to be out of character.

At a Press conference yesterday Mr Dennis said officers had been unable to trace any of the missing man's friends or his distant family. Some relatives are believed to live in the north of England.

Mr Dennis said: "Roy was not well at the time of his disappearance and he would not have been able to walk far or without a stick.

"He could have gone missing for personal reasons and does not want to be found. He could have committed suicide. He could have been the victim of a serious crime. All these areas are open to us.

"As the days go by, we are becoming more certain something suspicious may have happened."

Mr Chalmers, who used to sell glasses for a living, was described as about 6ft, 13st and of medium build. He has a pale complexion, silver-white hair and is clean shaven. He was wearing a dark bomber jacket, grey trousers, a light checked shirt and possibly brown leather shoes, a sovereign ring and a gold watch.

Anyone with information should call Brighton police on 0845 6070999, quoting Operation Herne.