The Justice Secretary is to unveil changes to the system of privileges in jail with the aim of ensuring that perks are actively earned.
John Massey escaped from Pentonville prison yesterday evening. The public are urged not to approach him, but to call 999 if they see him.
Prison officers across England, Scotland and Wales have returned to work after their walkout over changes to their retirement age.
A Prison Service source suggested the prison van ambush would probably involve one of the escapees having access to a smuggled mobile phone.
A phone call could then be made or a text sent to let the armed gang know which prison van they were in and so which vehicle to target, among the number of vans making their way from jail to Manchester Crown Court.
Police attention is focused on a green Saab saloon close to the prison van where around 9am this morning two inmates were helped to escape.
Witnesses reported seeing the van stopped by three men in a green car wearing balaclavas.
The raid took place just off the same stretch of road as a similar attack on a prison van.
Liverpool gangsters Tony Downes and Kirk Bradley escaped in the ambush in July 2011 as they were being taken from Strangeways jail to their trial al Liverpool Crown Court.
A witness has told Granada Reports she saw five men try to escape the scene in Regent Road in a dark-coloured car. She said they couldn't get through traffic and fled on foot. Some were wearing balaclavas.
The prison van came under attack shortly after 9am on Regent Road, Salford, a main road into Manchester around half a mile from the city's crown court and Strangeways prison.
A large number of officers have been deployed after two prisoners escaped from custody when a prison van was attacked, Greater Manchester Police said.
– Chief Superintendent Kevin Mulligan, Greater Manchester Police
To reassure those that live nearby there is a significant police presence in the area.
At this stage we do not believe that there is any ongoing threat to the community and we would appeal to anyone who has any information to contact the police as soon as possible.
Two men are believed to have been released from a prison van after it was attacked on Regent Road in Salford, Manchester, police said.