A paedophile pensioner was arrested after his own wife posed as a 14-year-old girl to trap him.

Former pub licensee David Anthony Roberts (69) even performed a sex act on himself in front of his computer webcam thinking a child was looking at him.

"But what he didn't realise until long after police had arrested and interviewed him was that the person watching was his own wife who was on her computer in the next room," prosecutor Martyn Kelly told Cardiff Crown Court yesterday.

Cheryl Roberts had been married for almost 20 years to the man psychiatrists now say might have a brain disorder, which causes him to be an exhibitionist.

But she became suspicious in 2008 about the amount of time he was spending in front of his computer screen.

How he was caught

When the machine pinged one day while he was out, she read the message which had popped up. It said, 'You are a f'''''' beautiful b''''' and was signed Corkyu00a0a name she knew her husband used for himself.

As a result of what she found, she went to her own computer and created profiles of girls aged 14 and 15 and was able to start having conversations with her husband, as a young girl.

Cheryl called the National Society for the Prevention of Cruelty to Children and then the police.

When police searched his computer, they found indecent images of children.

At a police station, he admitted he would have been prepared to have sex with the 14-year-old. The couple are now divorced.