Park kindly provided a clear image of his face during the burglary

Stills of serial raider Benjamin Park, 19, of Cambridge, were sent to an email address so even when he stole the computer, the images could be found.

Police said it was a "brilliant idea" of software engineer Duncan Grisby, who set it after a previous burglary.

Park was given an 11-month jail term by magistrates in Cambridge on Tuesday after admitting burglary.

The burglary was a real violation of my private space but at least he got caught Duncan Grisby

"I was burgled three years ago and was annoyed at the time because I had thought about setting this system up then, but hadn't got around to it," said Mr Grisby.

"I was relieved it did what I'd intended it to when I was burgled again. It was nice to catch him in the act - but it didn't stop him from stealing my things.

So how does it work?

"The burglary was a real violation of my private space but at least he got caught.

"I just wish he'd got a longer sentence."

Mr Grisby said the system was easy to set up. "There are lot of products for Windows that you can use to do this - though I used some free software and wrote some extra software myself."

Police described Mr Grisby's idea as "absolutely brilliant".

SAY CHEESE Have a look at some of the snaps that won't be making it into Ben Park's photo album

"The webcam was set up in his computer and began filming once it registered motion. It captured every movement Park made," said Det Sgt Alan page, head of Cambridgeshire Police Burglary Squad.

"At one point he stared into the computer as if it might be making a noise or something to make him suspicious.

"He then stole the computer but it didn't matter because Mr Grisby had set it up so that as it was recording it was sending the images to an email address.

"When the break-in was discovered Mr Grisby simply gave us the email address and we were able to watch several minutes of footage and say, `That's Ben Park'.

"Mr Grisby is an extremely bright man. He'd set this up because he'd been burgled some years ago and the quality was superb.

'Better than alarm'

"It was better than a burglar alarm and when Park initially denied breaking in to the property we were simply able to show him the footage."

Magistrates heard Park, who has more than 13 previous convictions for theft, had stolen computer equipment and other property with a value of nearly £4,000 from Mr Grisby's study.

He committed the offence in February while on bail after being charged with an attempted burglary in Ely, Cambridgeshire, in August.

"The webcam made our job really easy," added DS Page. "It was a pleasure to show him the pictures and see his expression when we interviewed him."

So how did Duncan Grisby catch the burglar in the act?

There are many commercial software packages available to capture images from a web cam and send them to an e-mail address or over the internet to a web page.

But Mr Grisby took a more Do-It-Yourself route which requires some technical knowledge.

He used a cheap video camera which is plugged into a video card inside his PC to capture the images.

Software running on the PC - which must be left switched on and have an "always-on" internet connection - detects motion and activiates a separate program written by Mr Grisby.

That program instructs the computer to grab photos from the video camera - up to five stills per second - and then send them to an e-mail address or over the internet to a webpage where they are stored for viewing.