Unless you've taken part in a major riot recently, the chances are you're not particularly well acquainted with CS gas.

Shoppers at Wickes in Tallow Hill, Worcester, certainly didn't know what was going on when the DIY store started filling with smoke.

All they know is that staff told them to leave immediately.

It was perhaps only afterwards that they discovered they had had a lucky escape. Thanks to the quick thinking of staff, the building was evacuated in short order and only one person fell victim to what was later discovered to be a CS gas capsule.

CS gas is nasty stuff. Used by police forces around the world to suppress disorder on the streets, its incapacitating effects include streaming eyes and a burning nose and throat. It can even prove fatal to people who suffer from asthma.

Exposure would have been extremely unpleasant to the Wickes victim - not to mention the distress and inconvenience caused to those shoppers who were forced to evacuate the store.

The incident can therefore not be dismissed as a mere prank. The capsule was almost certainly set off for someone's amusement, but a device with such potential for harm is in a different league to the stink bomb which may have been used in an earlier, more innocent age.

It marks a worrying trend after another CS capsule was set off in Worcester's main mosque, just up the road in Tallow Hill, on Sunday evening.

The sooner the sick CS prankster is caught by police, the better.

Otherwise a lot more people may find themselves more knowlegeable about the stuff than they would like.