A train guard accused of beating a retired businessman to death on his boat admitted throwing the body overboard, a court heard.

David MacBride, 45, who is charged with the murder of Robert Saint, told the jury at Lewes Crown Court the wealthy pensioner died in a tragic accident at sea.

He said he found Mr Saint, 70, unconscious in the engine room of his 42ft motorcruiser, The Sundowner, after losing control of the boat. MacBride said he panicked and threw Mr Saint's body into the sea because he feared no one would believe he was not to blame.

In his distress he had covered Mr Saint's head with two plastic bags in a bid to stop blood getting on the carpet of the luxury vessel.

The prosecution alleges MacBride, of Bramber Close, Bognor, had become obsessed with buying The Sundowner and bludgeoned Mr Saint to death after pretending he had the £119,000 asking price in cash. He said he had found the money on a train.

MacBride agreed to buy The Sundowner, moored at Birdham Pool marina, near Chichester, in September last year.

Retired businessman Mr Saint, of Horsham Road, Steyning, went missing after the meeting and his body was washed up on a beach on the Isle of Wight two weeks later.

A post-mortem revealed the widower died of multiple head injuries.

MacBride, who denies murder, told the jury Mr Saint died when he accidentally fell against machinery in the engine room and hit his head.

MacBride said the fatal injuries must have happened when he momentarily lost control of the vessel as it was suddenly rocked by waves.

He said he had sailed the boat through a lock and into the Channel before he and Mr Saint chatted.

Mr Saint's son, Glen, sat in court as the defendant said: "He was up at the front talking to me. He mentioned something about one of the engine temperature gauges not being right.

"He disappeared out the back into the engine room. I was curious and left my seat. Somehow the boat seemed to get side on to the waves. It was choppy. It was rocking.

"I ended up on the floor. I came round and struggled down to the engine room. I noticed Bob on the floor. He was on his back. I checked for a pulse but there was nothing.

"That is when the panic started. I noticed some blood behind his head. I am very squeamish. I tried to move him and as I did so the back of his head knocked into the engine.

"I tried to get my head together. All I could think was that I had moved the body and that would make it look a lot worse. I did not think anyone would believe me.

"I put a couple of Tesco bags over his head to stop the blood going all over the place.

"I managed to move him upstairs and over the side. I thought the problem would go away."

MacBride, who was giving evidence on the eighth day of the trial, said the accident happened after he had paid for the boat in cash, which he found on board a train weeks earlier.

He said Mr Saint agreed to go on a trip with him to help MacBride get to know the boat, which he had bought as a surprise birthday and wedding anniversary gift for his wife.

MacBride told Jonathan Fuller QC, defending, that he also tossed the money overboard.

He said: "When I found it it was like quite a few Christmases rolled into one. I was on an early train from Bognor to London Victoria.

"I was going through the empty train when I saw a holdall on a rack. I opened it and saw a layer of money. I fell for the temptation."

MacBride sailed the boat back to Itchenor, also near Chichester. The next day he tried to wash the blood off it.

He originally told police he had dropped Mr Saint at Portsmouth.

The trial continues.