The Prime Minister grimaced and exclaimed “you are joking” as he was shown a body scan from a prisoner who tried to smuggle contraband into jail in a Kinder egg hidden inside his body.

Boris Johnson toured HMP Leeds, an inner-city Victorian jail, where staff told him the introduction of a state-of-the-art scanner had led to a reduction in drug smuggling and therefore violence.

Mr Johnson spent around 90 minutes touring the prison in the Armley area, where he talked to managers, guards and inmates.

He was given a demonstration of an £80,000 torso and body scanner which is used on new inmates, recalled prisoners and those who have been to court, and which uses sophisticated X-ray imaging to detect contraband.

Boris Johnson visit to HMP Leeds
An image on the torso and body scanner that was shown to Prime Minister Boris Johnson at Leeds Prison

Since it was introduced in December, 4,500 scans have been undertaken and around 60 seizures of drugs, tobacco or mobile phones were made.

Mr Johnson was shown a stored image of a body scan which showed a Kinder egg secreted inside a prisoner, which was later found to contain tobacco and he exclaimed: “You are joking.”

Tobacco has been a contraband item since smoking in jail was banned.

Another stored image on the scanner clearly showed one mobile phone in an inmate’s stomach that he had swallowed, plus another two in his bowel.

Mr Johnson walked through the prison before meeting senior management and joked he had been shouted at on his way through – claiming it was a supporter.

He then walked through the prison rotunda, up spiral stairs and into a meeting room where he shared a cup of tea with prison warders, then walked down A wing to meet one of the jail’s 1,100 inmates.

Boris Johnson visit to HMP Leeds
Prime Minister Boris Johnson talks with prison staff by a scanning machine during a visit to HMP Leeds after the announcement of �100 million investment to boost security and cut crime in prisons, with the warning that jails cannot become “factories for making bad people worse”.

No details were given about the identity of the inmate, or what offence he had committed.

That wing was for prisoners who have volunteered to take part in a drug treatment programme.

One sign on the wall of the prison stated “HMP Leeds, protecting the public since 1847” and the most recent inspection two years ago stated that the local Category B jail with 667 cells was one of the country’s most overcrowded.

In the 2017 inspection, 60% of prisoners reported that drugs were easy to obtain.

Following the visit, Mr Johnson said the Government will spend £100 million on scanners “to protect the staff and to stop the prisoners bringing in, to put it bluntly, in their alimentary systems, drugs and mobile phones, which greatly degrade the life in prisons”.