Four men were yesterday each jailed for six years for a £1.8 million raid which was carried out like a "military operation" at a Tamworth bank cash handling centre .

The thieves, who escaped with the cash after ramming a stolen skip lorry into a wall "must have had inside help", Stafford Crown Court was told.

Most of the money has not been recovered. Judge Mark Eades said he was satisfied other people were involved.

Mr James Burbidge QC, prosecuting, said night staff were inside counting money "when there was an explosion and the wall began to crumble" at the Royal Bank of Scotland's cash counting facility at Amington Industrial Estate in October last year.

He said: "A worker saw someone with a black helmet on climb through a hole. People were screaming and shouting and fleeing from the room. "One woman jumped with fear when she heard the bang," he said.

"There was significant planning, trust, deceit and secrecy in this conspiracy and a risk analysis was made.

"Money stored in cages amounted to £3.5 million - and £1.8 million was taken.

"The facility was not widely advertised but gaining knowledge about a significant amount of money must have come from inside information," he said.

The crime required a considerable amount of preparation.

"The attackers would know about a shift system and that people would have been working there at night," he said. Before the court were Kenneth Bourne (26), of Petitor Close, Terrance McGurk (29), of Alton Close, Karl Powell (26), of Winston Close and Dean Lindon (29), of Mawnan Close, all Coventry.

They pleaded guilty to conspiracy to burgle. Judge Eades told them: "This was a slick, well-planned and thoroughly professional burglary run with the precision of a military operation.

"Those involved had first class intelligence in particular relating to the lay-out, shift times and procedures at Kestrel House. There was careful planning and comprehensive reconnaissance.

He said: "A large amount of money was stolen and almost all of it is still outstanding. It is also clear that the way this burglary was carried out engendered in those who watched a climate of fear.

"There was a latent threat of force. " I am quite satisfied that others were involved but you four were at the height of the conspiracy and played vital and important roles."

Mr Burbidge said when the men smashed through a chain link security fence with the skip lorry "they knew exactly where to go."

The lorry was slowly reversed up to the wall then driven back at speed to the exact spot.

"The lorry rammed a car out of the way and collided with two other vehicles before hitting the wall," he said.

A security video showed terrified staff running out and the burglars stuffing money into yellow holdalls.

Millions of pounds pass through the sorting centre weekly from the Royal Bank of Scotland, NatWest Bank and Tesco's.