A teenager is recovering from a stab wound to his chest after an argument outside the Texas Chicken take-away in Uxbridge Road, Hammersmith, escalated in broad daylight.
An argument broke out between the 15-year-old and his three friends and another group of young people, aged between 14 and 16, which got out of control when the rival gang pulled a knife and stabbed the teenager in the chest.
London Ambulance Service sent paramedics racing to the scene.
Hammersmith CID Detective Constable Gareth Rees was one of the first to arrive at the take-away, where medics were already treating the Asian teenager. "He was very shocked about what had happened and he was upset," said DC Rees. "His friends were still with him when I arrived."
The boy was taken to St Mary's Hospital in a serious, but stable, condition where he received further treatment.
DC Rees said police were still unsure what the argument was about and how it led to a stabbing but he deplored the violent incident, which happened at 4.420pm on February 8.
"It is shocking that this sort of thing could happen with members of the public going about their business in the middle of the day," he said.
Police arrested two 15-year-olds from the Lime Grove area on suspicion of GBH in the days following the stabbing and they have been bailed to return to a police station in March.
But DC Rees said police were still looking for another teenager, described as a dark-skinned black male, 5ft 6ins with a medium build, and he appealed for witnesses to come forward.
"We are keen to speak to a youth aged approx 14yrs in connection with this incident," he said. "We believe that he is a local youth from either the Shepherds Bush or White City area."
The stabbed teenager has since returned home and is expected to make a full recovery.
If you have any information, call DC Rees on 020 8246 2504, or call Crimestoppers in confidence on 0800 555 111.