A 16-year-old boy has been murdered at a packed London train station.

Louis Johnson was stabbed to death in a violent attack that lasted 40 seconds on Monday afternoon.

He entered East Croydon station at about 4.30pm through the Ruskin Square ticket barrier and was attacked minutes later.

British Transport police (BTP) said that while he was on the overbridge in the station, he met someone who immediately pulled out a knife and stabbed him.

Emergency services were called at 4.45pm but despite the efforts of medics, including an air ambulance team, he died.

DCI Sam Blackburn said: “This was a senseless killing at an extremely busy time of the day, and my thoughts are with Louis’ family at this painfully difficult time.

“For such a young man to lose his life in these circumstances is truly devastating, and I would like to reassure everyone that a thorough investigation is well under way.”

He urged anyone with information to contact BTP.

“The incident was over within a matter of 40 seconds, but I know many other passengers or members of the public would have seen what happened.

“Importantly, if you have any mobile phone or dashcam footage of the East Croydon area either just before, during or after the attack, we want to hear from you.”

The boy’s family have been told and are being supported by police.

BTP said there would be increased patrols in and around the station on Tuesday.

A 16-year-old boy was detained in Balham in connection with the murder, police saod on Wednesday morning. But details of the arrested boy’s alleged involvement in the incident have not yet been disclosed.

Anyone with information can contact BTP by sending a text to 61016 or by calling 0800 40 50 40 quoting reference 395 of 27/01/2020, or contact Crimestoppers anonymously on 0800 555 111 or online.