A schoolboy was killed “in the blink of an eye” by a stranger who stabbed him in the neck at the New Year's Eve fireworks display in Primrose Hill after accidentally colliding with a group of teenagers, the court heard

A schoolboy was killed “in the blink of an eye” by a stranger who stabbed him in the neck at a New Year's Eve party with fireworks, a court heard.

Sixteen-year-old Harry Pitman was playing with his friends when he bumped into another group of teenagers on London's Primrose Hill, where crowds had gathered to watch the annual performance on December 31 last year.

A 16-year-old boy, whose name cannot be disclosed for legal reasons, is said to have pulled out a knife and fatally blown him in the neck after an argument between Harry and his friends.

The boy, now 17 years old, denies murder and possession of an offensive weapon.

At the start of his trial at the Old Bailey on Tuesday, prosecutors said the attack lasted barely 20 seconds but was recorded in full by someone filming nearby.

Police officers conduct a search on Primrose Hill in Camden, north London, where the 16-year-old died

Jurors were told the defendant admitted stabbing Harry, but they must decide whether he acted in self-defence, caused the stab wound accidentally or whether he intended to kill or seriously injure the teenager.

Prosecutor Jocelyn Ledward KC said: “Every year, numerous citizens gather on Primrose Hill to celebrate the New Year.”

“But last year's New Year's Eve celebrations turned into tragedy in the blink of an eye. 16-year-old Harry Pitman was stabbed once in the neck.

“He died almost immediately as a result of this single but fatal injury.”

“A single but fatal injury caused by a knife that the defendant, who was only 16 years old at the time, had brought to the crime scene.”

Jurors heard that uniformed police officers were at the viewing point in the “upmarket” north London area that evening to control the crowds that had gathered to watch the fireworks.

Harry and the defendant were “complete strangers” and went there with different groups of friends, Ms Ledward said.

Shortly before the confrontation, a witness saw Harry apparently fooling around with his friends, trying to see how high he could kick in the air.

Harry Pitman, 16, was playing with his friends when he accidentally bumped into another group of teenagers

People attend a vigil at Downhills Park in the West Green district of Haringey, London, for 16-year-old Harry Pitman.

Police officers conduct a fingerprint search on Primrose Hill on New Year's Day

However, while attempting to do so, he lost his balance and collided with a member of the group behind him, the court said.

Ms Ledward said: “What happened next happened very quickly, within a very short period of time, in fact less than 20 seconds.”

Harry initially got into an altercation with a friend of the defendant before the defendant pushed towards him and pulled out a knife when he intervened in the fight.

Jurors were told the video shows the defendant moving his arm downward in an “arcing motion” – with a “shiny object” in his hand catching the light. The prosecution says this was the knife.

Severely injured and bleeding profusely, Harry stumbled to a group of police officers nearby and pleaded for help while the attacker reportedly fled the park. The 16-year-old had lost a “catastrophic” amount of blood and died at the scene.

Police said the murder weapon was never found, but traces of the defendant's DNA were found in a knife sheath that fell to the ground nearby.

Five members of Harry's family sat in the courtroom and watched the opening of the prosecution.

The process continues.