Three others were also attacked
Four people have been stabbed at the Notting Hill Carnival, with one man fighting for his life in hospital.
Emergency services were called to Wornington Road in Kensington and Chelsea at 4.25pm on Sunday, the day the festival is dedicated to children and families.
A man was arrested on suspicion of causing grievous bodily harm. Minutes later, police were called to another stabbing on Portobello Road, taking one person to hospital.
Two men were also stabbed on Ladbroke Grove and were taken to hospital.
The men were among 345 people treated by ambulance workers at the carnival, with 43 of them taken to hospital.
Police said they had arrested 47 people by 6.30pm - two for alleged sex offences, 37 drugs offences, 13 counts of possession of offensive weapons and alleged theft and public disorder.
More than a million people were expected to attend the carnival on Sunday.