A third person has been arrested by detectives investigating the escape of a murderer from custody.

A 25-year-old man from Norris Green, Liverpool, was detained on suspicion of perverting the course of justice after armed men freed Shaun Walmsley on Tuesday, police said.

A police car is parked outside Aintree University Hospital
A police car parked outside Aintree University Hospital earlier this week (Peter Byrne/PA)

Two people arrested on Thursday for allegedly assisting an offender have been released pending a decision of whether to take further action.

Walmsley, 28, from Liverpool, went on the run when two men armed with a knife and a gun confronted prison officers guarding him at Aintree University Hospital during a visit from HMP Walton on Tuesday afternoon.

A 27-year-old man and a 26-year-old woman at a property in Norris Green, Liverpool, on Thursday evening in connection with the escape.

A gold-coloured Volvo believed to have been used was found (Merseyside Police/PA)
A gold-coloured Volvo believed to have been used was found (Merseyside Police/PA)

Walmsley and the men fled in a gold Volvo with the registration number MW02 XHE, which detectives found in the Fazakerley area of Liverpool.

Detective Superintendent Natalie Perischine said: “The CCTV shows that the people involved in the actual incident were in a very close huddle and we know that although a gun and knife were used by the offenders, they were not blatantly on show to other people walking by.

“These witnesses may not have realised what was going on. They may have thought it looked a bit odd, but probably wouldn’t have thought anything of it.

Shaun Walmsley was being held at HM Prison Liverpool (P)A
Shaun Walmsley was being held at HM Prison Liverpool (P)A

“We do know that the gold Volvo was blocking the rear of the car which was meant to take Walmsley back to prison, and this was making access to a roundabout at the hospital difficult and one delivery driver was forced to mount the kerb to get past.”

The officer appealed for the public to look at the images and to contact the police with information.

“I would like to reiterate that Shaun Walmsley and the two others involved in the incident are dangerous individuals and we will be relentless in our pursuit of them,” she added.

Police warned the two accomplices were believed to be armed.

Walmsley was serving life with a minimum of 30 years for the murder of Anthony Duffy, 33, in May 2014.