They would pump gas into cash machines before igniting it, setting off an explosion to blow the machine out of the wall and allow them to cut into the safes inside with angle grinders.

After a string of raids police set up Operation Cass to track them down and they were caught in February this year, having used a holiday park in North Wales as their base of operations.

At 4am on Friday, February 14, they pulled up outside a post office in Oldham in a stolen car, whereby police intercepted them as they started their crime.

Sgt Rick Castley, of Greater Manchester Police’s Serious and Organised Crime Group, said: “When they were arrested, they had gas canisters in the back of the car and all the cutting equipment.

“We had a surveillance operation, we were behind them that day. It was clear what they were going to do.”

Sgt Castley added the equipment and techniques being used marked the gang out, combing CCTV, looking for offenders in similar clothing in different incidents. They examined the roles they played and the cars they used.

“It is quite unique, people blowing up ATMs,” Sgt Castley said. “There are not many people with the expertise or knowledge. You are only looking at one or two teams doing it in the region. By the nature of the methods used, we identified 14 offences as being linked.”

Detectives also trawled telephone data after mapping raids.

“We looked at the offending patterns,” Sgt Castley added. “It was in Stockport, some of it, then Cheshire and North Wales.”

“They would then commit the offence, then go back to Wales to be out of the area,” Sgt Castley said. “If they were travelling over several boundaries – covered by different police forces – they would think they were safe. They might be well known in Manchester, but not Cheshire or North Wales.”

Lewis Murkin, 33, of Daresbury Close, Stockport; Philip Clarke, 32, of Woodland Avenue, Manchester; Ryan Wilson, of 31, of Chelford Grove, Stockport; and Michael Cash, 30, of Weldon Crescent, Stockport, pleaded guilty to conspiracy to cause an explosion likely to endanger life or property; and conspiracy to commit burglary with intent to steal at Manchester’s Minshull Street Crown Court.

Martin Goldstraw, 43, of Tarporley Close, Stockport, pleaded guilty to conspiracy to commit burglary.

The five men will be sentenced by Judge John Potter at a later date.