A 16-year-old boy was arrested today in connection with the stabbing of a 14-year-old.
The injured boy, stabbed in south London on Tuesday, remains in a critical condition in hospital today.
Scotland Yard said the 16-year-old was arrested this morning and is in custody at a south London police station.
The teenager was attacked in Great Dover Street, Southwark, after a row with a group of youths, police said.
Officers were called to the scene just after 5pm.
He was taken to the Royal London Hospital by air ambulance, Scotland Yard said.
The youngster was stabbed twice, once in the stomach and once in the chest, it is believed.
Witnesses said the row spilled over from football pitches nearby.
The victim was attacked behind a student halls of residence in Great Dover Street, they said.
He was given first aid by staff at the Sidney Webb House, which houses 700 students from King's College London.
Many were packing up their belongings to return home after finishing their exams.
One, a first year mathematics undergraduate, told of her shock.
"It's a nice area - you don't expect something like that to happen here," she said.
A Met Police spokesman said: "It is believed the victim was involved in an altercation with a number of youths prior to the incident."
Police have appealed for witnesses to come forward.
The incident took place near the junction of Great Dover Street and Becket Street.