It is remains unclear why Alan Pennell was driven to murder

The 16-year-old, detained for life for the murder of Luke Walmsley, 14, at Birkbeck College in North Somercotes, Lincolnshire, was obsessed with violent films and kept a collection of knives.

On the day that he fatally stabbed Luke in the heart, he had earlier held the lock-knife to the throat of another classmate during an argument about football.

The reason behind the murder was never clear, although the prosecution pointed to a fight between Pennell's best friend and Luke in the weeks prior to the killing.

Pennell also discovered that Luke had passed notes to his (Pennell's) girlfriend during lessons, that talked about a fight between the pair, prosecutors said.

Mother's death

Pennell had earlier fallen out with Luke following the break-up of a brief relationship with Luke's 12-year-old sister.

Pennell began boasting that he would kill the younger boy. He appeared jealous of Luke, who was a popular sportsman with a happy family background.

Pennell's mother had been tragically killed in a car crash, along with her boyfriend, when the boy was just four.

With his father often away working as a lorry driver, Nottingham Crown Court heard that Pennell was often left to his own devices and spent much of his youth getting drunk and hanging around with a succession of girlfriends.

Pennell told the court that he had felt "gutted" when he heard Luke had died from the stabbing, adding that he knew what it felt like to lose someone because of the death of his mother.

Threats

Friends who had heard Pennell's threats to kill Luke had believed they were empty.

On the day of the killing, they told him to put his knife away when he began twirling it round his fingers outside a classroom.

But as the murderer's best friend told the court: "Once he gets it into his head that he's going to do something you can't stop him.

"There are playground fights aren't there, but I didn't think anything like that would happen."

Witnesses said the stabbing of Luke Walmsley was sudden and had appeared little more than a punch.

But the knife punctured the 14-year-old's heart and he had no chance of survival, despite attempts at the scene by paramedics to resuscitate him.