The arrest follows the death of Hazrat Wali, who was attacked in Twickenham on Tuesday.
A 16-year-old boy has been arrested after a teenager was stabbed to death on a playing field in south-west London.
Police found Hazrat Wali, 18, fatally injured in Craneford Way, Twickenham, at 16:45 BST on Tuesday.
The Richmond upon Thames College student was taken to hospital but died an hour later.
The Met said the 16-year-old boy had been arrested on suspicion of murder and remained in custody.
The principal of the college Jason Jones has paid tribute to Mr Wali, who was from Notting Hill, saying he would be remembered “fondly as a bright and polite young man, well liked by staff and his close-knit group of friends”.
Dr Jones added: “This loss is sure to raise many emotions, concerns, and questions for our students, parents, staff and local community.
“Safety remains our number one priority and we will continue to do all we can to keep our students safe at college.”
Scotland Yard said a post-mortem examination was set to take place on Friday.
The force has appealed for anyone with information or footage of the attack to get in touch.
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