Its remit is to target organised crime, street gangs, armed robbery, drug and gun smugglers and kidnappings.

In their first year officers on the unit had made more than 100 arrests, recovered almost four tonnes of cannabis, 50kg of cocaine, several firearms, including an Uzi sub-machine gun, and seized more than £300,000 in cash.

Dirty Harry, directed by Don Seigel, was itself loosely inspired by the unsolved Zodiac killings, which left a trail of fear across California in the late 1960s.

At least five people were killed and two others wounded by the killer who taunted police with cryptic letters sent to a newspaper.

The killer was never caught.

A West Midlands Police spokesman said the Co-op blackmail investigation resulted in a man in his 30s being arrested and charged in connection with the inquiry.

He will appear in court next week.