A gang feud was to blame for the fatal stabbing of a Mitcham teenager during last year’s Boxing Day sales, a court has heard.

Seydou Diarrassouba, 18, from Phipps Bridge, bled to death outside Foot Locker in London’s Oxford Street after he was stabbed twice in the chest on December 26, 2011.

The teenager had been stabbed through the heart with such force that the knife blade had broken off at the hilt.

Jermaine Joseph, 23, a former gang member who used to live in Mitcham but who moved to Conway Road in Haringey in April 2011, has been charged with his murder alongside Thulani Thomas Khumalo, 20, from Etherley Road in Haringay.

Appearing at The Old Bailey yesterday, the court heard the fatal stabbing happened after the men, who had a history of "bad blood", spotted each other in the street.

Mr Joseph was followed into Foot Locker by Mr Diarrassouba, who was then stabbed twice by Mr Joseph so quickly no one realised what had happened. Mr Diarrassouba staggered outside of the shop and collapsed on the pavement where he died.

Opening the trial Mr Mark Heywood QC, prosecuting, said: "The grievance was evidently a deep seated and powerful one.

"It led almost instantly to ugly, brutish violence in broad daylight in a packed street in the busiest shopping day of the year."

He added: "You may have thought that one of the few times and places in this country where people could go about their business in peace was in the west end of the capital on Boxing Day.

"But that isn't the case when groups of young men ill disposed to one another meet and some of them like these defendants are armed with sharp and dangerous weapons."

Mr Joseph told police he had acted in self defence because he feared being attacked, while Khumalo denied involvement in the stabbing.

The court also heard how Mr Diarrassouba, a former business student at South Thames College and Rutlish School in Merton Park, was a member of the All About Money (AMB) gang that had become suspected of robbery, violence and of having access to weapons.

In his statement to the police, Mr Joseph said Mr Diarrassouba’s street name was ‘Nutz’ and that he was a senior member of the AMB with a reputation for violence and stabbing.

Mr Joseph and Mr Khumalo both deny murder claiming self-defence. The trial, which is expected to last five weeks, continues.