A woman told a jury how she watched her lover fatally stab her husband in a horrific knife attack.

Tony Banks was slashed at least five times around the head and neck with a kitchen knife when he turned up at the flat the lovers shared in Mill Road, Lewes, in a drunken rage, Lewes Crown Court heard.

His estranged wife Barbara told the jury her husband was climbing through the kitchen window when he was attacked by her boyfriend David Armstrong.

Mr Banks, 43, a father-of-two and a grandfather, died an hour later at the Royal Sussex County Hospital, in Brighton. Armstrong, 39, has denied a charge of murder.

The court heard how Mrs Banks and her husband had separated last October after 24 years of marriage when she started an affair with his friend Armstrong. The two men had worked together as kitchen fitters, regularly had drinks together, went for meals and had shared a holiday.

Mrs Banks described her husband as being "devastated" when she left and said he had twice turned up at the lovers' ground-floor flat.

On the second occasion she jumped out of the window to get away from him and stopped a bus. She then called police.

The court heard her husband smashed up the flat.

Mr Banks was charged with aggravated burglary and released on bail on condition he kept away from his estranged wife.

A month later, on the evening of December 15, Mr Banks, of Cowfold Road, Whitehawk, Brighton, began making a series of phone calls and sending text messages to the couple.

He pleaded with his wife to return to him and sent messages to Armstrong. One said: "Leave my wife alone, she will never be happy with you."

Armstrong started to ring 999 but Mrs Banks stopped him because she did not want her husband arrested and kept in jail over Christmas.

At 3.30am the couple were woken by the noise of banging and shouting. Mr Banks, who was carrying his fishing knife in his back trouser pocket, was trying to kick down the front door. He then picked up a metal dustbin and smashed it through the kitchen window.

He was shouting to Armstrong: "Leave my wife alone" and calling him a pervert. As Mr Banks, who had been drinking and had taken anti-depressants, tried to climb past a fridge-freezer, Mrs Banks said she saw Armstrong had a knife in his hand.

She told the jury: "I remember going behind Dave and then I saw his arm come up. He had a large kitchen knife in his hand. He stabbed Tony three times in the neck and then the back of his head. Tony fell out of the window."

The court was told neighbours, woken by the noise of a woman screaming hysterically, saw Mr Banks bleeding heavily from a neck wound before falling to the ground.

While the couple waited for police and an ambulance to arrive, Mrs Banks said Armstrong asked her how she felt about what he had done.

She said: "I said something like 'You didn't need to use the knife.' I think he asked if I was going to stay with him."

She said her affair with Armstrong ended that night.

The jury heard after his arrest Armstrong told detectives he had only acted in self-defence.

He said it had been dark and he was frightened and in fear for the safety of himself and Mrs Banks.

He had prodded him three or four times through the curtain to stop him coming into the flat.

Richard Anelay QC, prosecuting, told the jury the Crown accepted Mr Banks had threatened Armstrong, including saying "You are a dead man" but said he acted with undue force.

He said: "He must have known the police would arrive shortly. He could have pushed him back out of the window.

"It was not necessary to kill Tony Banks or to do him really serious bodily harm."

The trial continues.