A convicted killer serving a life sentence for murdering his cousin’s son features in a threatening video taken from inside a prison cell on an illegal mobile phone.

John ‘Boy’ Ward shot dead 21-year-old Thomas Ward on the traveller site in Dyes Lane, Stevenage, in 2013 as part of a 30-year feud between two families.

The 34-year-old is currently serving a minimum 32-year sentence in a Kent prison, but a video of him and another man has been released online via WhatsApp, with the other prisoner saying: “When I get out you’re going to be terrorised.”

The chilling footage, seen by the Comet, sees the two convicts topless, laughing and jeering at the camera. It makes a mockery of prison security, with measures such as body scanners, high sensitivity metal detecting wands and intelligence-led searches failing to detect the device.

It is a criminal offence to take a mobile phone into a prison, or transmit sounds or images from within a prison using a mobile phone.

The two men look set to be stripped of their privileges and face up to two years being added to their sentences.

A Prison Service spokesman said: “This behaviour is totally unacceptable. These offenders are being investigated and may face further disciplinary action.

“It is a criminal offence to bring a mobile phone into prison, and we have measures in place to detect them.

“But we have to look at new ways of blocking mobile phones, as well as equipping prison officers with the right tools to tackle this issue.”

Legislation is being introduced to allow the Prison Service to apply for a court order to compel mobile network operators to disconnect illicit mobile phones being used in prison.