A 16-year-old boy killed his mother's 33-year-old friend when she declared: "I love you", a Court was told today.

Maria Carter had repeatedly telephoned Dean Cullen after a holiday romance, jurors heard.

Cullen, now 18, went to the woman's home to try to break off the affair and she answered the door wearing just a nightie.

When she put her arms around him on the sofa he admitted throttling her with a chain and stabbing her twice.

An autopsy later revealed Ms Carter had suffered 19 stab wounds.

Police later revealed that Ms Carter was due to move to Bradford to live with her fiance and put posters throughout the district about her killing.

Cullen, now 18, wept as he gave evidence at London's Middlesex Guildhall Crown Court.

He told how his affair began when he stayed with Ms Carter during a holiday at a caravan park in Essex in 1999.

He said the sexual encounter was unexpected and he felt awkward and did not know what to do.

"I felt scared. I'd never been in that situation before. She was twice my age."

The next morning, Cullen said he drank five bottles of beer in a park and told a friend what happened.

"I wanted to drink to get out of my head. I could not be near her by myself."

When they returned to London, Cullen would leave when Ms Carter visited his mother.

"I'd try to get out of the room, go somewhere else," he explained.

He said Ms Carter repeatedly rang him on his mobile telephone but he did not answer.

Later that year, Ms Carter became engaged to Steve Whitley from Bradford. She began to spend more and more time with Mr Whitley and would upset Cullen's mother by failing to meet her.

On January 17, 2000 he went to her home with a kitchen knife which the teenager claimed he carried after he was attacked by local youths.

"I wanted to tell her to stop letting Mum down, and to get the sexual thing off my mind," he told the court. "I wanted to tell her it's not going to happen again."

He went with two friends, a boy and a girl who waited nearby as he called at the house in Plumstead, south east London.

Cullen told the court that Ms Carter told him she loved him. He wept in the dock as he said he could only remember "a little bit" of what happened next.

"I put the chain around her neck," he said. "Then I stabbed her. I remember I stabbed her a couple more times at most. I thought I killed her because there was blood everywhere."

Cullen, of Plumstead, denies murder.

The trial continues.