Luke Walmsley was stabbed in the chest

The 16-year-old boy said he was annoyed and upset that Luke Walmsley had been passing notes to his girlfriend.

The teenager, who cannot be named for legal reasons, was giving evidence for the first time in the trial.

The teenager denies murdering Luke at Birkbeck School in Lincolnshire last November.

The teenager said he had never got on with 14-year-old Luke, whom he believed had been making threats to fight him.

He added: "I just wanted to say something to him to stop all this - him threatening me, saying things about my mum and bringing (my girlfriend) into it."

Sasha Wass QC, defending, said: "You said you wanted to put a stop to it. How did you think you were going to put a stop to it?"

He replied: "Just by threatening him."

'Accidental' stabbing

She asked him: "On Monday, 4 November, I think it's right that you took a knife to school.

"When you took that knife to school, what exactly did you have in mind?"

He replied: "Just to show it to him and scare him."

The actual stabbing was an accident, he claimed, with Luke walking into the knife.

Under cross-examination, the defendant said he could not remember anything about claims he had talked of stabbing Luke, possibly because he was drunk at the time.

The trial continues.