Illegal access to knives among young people remains a key concern for police, with dealers selling weapons to under-18s via social media.

One of the 12-year-olds accused of murdering Shawn Seesahai claimed he got the machete used in the killing from “a friend of a friend”, but police said there was some evidence that he had searched for knives online.

Detective Inspector Damian Forrest, who led the investigation, said: “The weapon was a large machete that really no person who doesn’t need it as a tool of their trade should have any reason to own.

“Obviously, originally it would be a gardening tool.

“Although the facts of this case mean we can’t say for certain how that weapon came into the possession of the suspects, there is some evidence that suggests that one of them had tried to purchase knives on the internet.”

In a separate case, 17-year-old Rayis Nibeel was found to have bought 65 knives online and sold them on for profit in the few months before he murdered Omar Khan, 38, in a dispute over drugs in Luton in September last year.

Last month police chiefs said that illegal dealers are selling weapons to under-18s via social media channels, including TikTok, Snapchat and those run by Meta.

Some teenagers, often those involved in drug dealing, want to buy large status weapons like zombie knives or machetes.

The national lead for policing knife crime, Commander Stephen Clayman, said the accessibility of knives online is “a really concerning picture” for law enforcement.

Official figures show that knife crime rose by 7% in England and Wales in the year to December 2023, compared with the previous 12 months, but the total 49,489 offences recorded remained below pre-pandemic levels.

Part of the increase was driven by a rise in knifepoint robberies, which went up by a fifth year on year.

Knife-enabled homicides stood at 239 last year, broadly unchanged on the 235 recorded in 2022 and also lower than pre-pandemic figures.

However, in the year to March 2023, 82% of teenage homicide victims were killed with a knife, compared with 73% in the previous year.

The latest official statistics show that West Midlands Police had the highest number of knife crime offences per head of population in England and Wales in the year to December 2023, ahead of the Metropolitan Police.