LONDON – A gang of armed robbers impersonating police officers tied up employees at a southern England security company and stole the equivalent of $43.5 million, the Bank of England said Wednesday in disclosing one of the largest bank heists in British history.

The money, about 25 million pounds in bank notes, was stolen overnight from a cash center at Tonbridge in Kent county, a bank spokesman said on condition of anonymity, according to bank policy.

No one was injured in the robbery.

The bank spokesman also said it was possible that more than $43.5 million was stolen, but the final figure will not be known until the security company completes its accounting.

The heist at Securitas Cash Management Ltd. began when some of the thieves, dressed as police officers, stopped the firm’s manager as he drove home Tuesday. The manager got into their car, which he believed to be a police vehicle, and was handcuffed by the robbers, authorities said.

At the same time, another team of thieves went to the manager’s house, saying he had been in an accident. The men convinced his wife and young son to leave the home and go with them.

The first team, with the manager in the car, met up with a white van and another group of thieves. The manager was placed in the van, which then headed toward the Tonbridge depot, police said.

The manager allegedly was told to cooperate or his family would be hurt.

Early Wednesday morning, the thieves in the van headed to the Tonbridge depot to meet up with accomplices driving a large white truck. The thieves tied up 15 employees and started loading cash into the truck, police said.

It is believed the thieves were in the depot for more than an hour before driving off with the cash, police said.

About an hour later, the staff managed to escape and call police.

“The staff were all very shook by what has happened,” said Detective Superintendent Paul Gladstone of the Kent police serious and organized crime unit. “This was a traumatic ordeal for the manager of the security depot, his family and all of the staff who worked there. They have all coped extremely well in the circumstances, when faced with threats and a gang of armed men.”

In December 2004, a raid at the Northern Bank’s Belfast headquarters netted thieves the equivalent of $46.1 million – the biggest cash theft in British history. Three men have been charged in connection with that robbery.

The Governor of the Bank of England has asked for a review of the security arrangements for the storage of bank notes. The bank spokesman said Securitas had already reimbursed them, and there will be no cost to Britain’s taxpayers.

The single-floored, squat brown building is windowless and just a 5-minutes walk from the center of Tonbridge, a small market town 30 miles southeast of London.

The building, on a small industrial estate, is surrounded by 6-foot-high steel fencing, and security cameras cover every entrance. Steel traps are in place to prevent unwanted vehicles entering the compound, which acts as a car park for employees. There are no signs to indicate the building stores vast amounts of money.