Knife concealed as pen found on a 12-year-old London schoolboy

With reports this week that British teachers have begun patrolling the streets in a bid to combat the so-called "knife crime epidemic", this video shows just how hard the task may be of identifying pupils carrying blades.

The clip shows a British man holding what looks like a pen which he claims he confiscated from a 12-year-old schoolboy in London.

The viewer understands why he took it when he pulls the ballpoint apart to reveal a 5.5-centimetre blade hiding in the shaft.

The man claimed the boy, a friend of his son, was showing off the knife before school and said he had bought it from a popular shopping website.

The clip was filmed back in January.