THE BUSINESS OF CRIME: There are now twice as many private security guards in the UK as 10 years ago

Jails have been privatised, and even police forces are hiring outside help. The jury may be out on the social effects of all this, but there's no doubt that the security industry has captured a lucrative market. Stephen Cook reports.

When Martin Richards got back to his detached house in Hadley Wood late on a winter evening, three masked men were waiting for him in the drive. They grabbed him in an armlock, forced him to open the door, and put him and his family through 10 minutes of terror that they'll never forget. Nine months later, they're still recovering from the trauma.

In our increasingly lawless society, there are hundreds, probably thousands, of us who can relate similar stories of violence. But what happened to the Richards family that night prompted another small but significant development in a pounds 4 billion industry that has grown inexorably over the past decade and is poised for yet more expansion.