By James Westhead BBC family correspondent

It is the modern parent's nightmare - the new stranger danger - your child lured to a meeting by an adult they don't know over the internet.

To find out how real that danger is we asked a team of specialist investigators to pose as a 14-year-old child in an internet chatroom.

The investigators Nigel Parsons and Marie-Louise McIlvenna work for the Answers detective agency and specialise in tackling internet crime.

It's typical grooming, luring and entrapping of a child Rachel O'Connell Cyberspace Research Institute

Keep your child safe: click here

They created a virtual identity - a typical 14-year-old girl they called Sydney.

For this investigation they followed strict rules.

Sydney would only visit innocently-titled chatrooms, would never approach others online, would never encourage sexual attention and would be non-committal and passive in online conversation.

We did not want to be accused of entrapping innocent web-surfers.

Nevertheless, during the two-week investigation, Sydney was approached by 30 men and even a middle-aged couple who apparently wanted a sexual encounter with someone they knew was a child.

The man was arrested by police

One man was persistent and messaged every night for a fortnight.

From the start he tried to persuade the girl to leave her home and meet him late at night.

She refused but he continued trying to develop the relationship, asking her probing questions about her sexual experience, fully aware she is a child of 14.

During the conversations, he asked Sydney if she had ever kissed anyone or seen a man naked.

He also told her how to erase her message archive and stressed he must not tell her parents or friends about their relationship.

'Classic behaviour'

We showed the transcripts of the exchanges to Britain's leading expert on internet paedophiles, Rachel O'Connell, director of the Cyberspace Research Institute.

She told us: "This is just the classic behaviour pattern of a paedophile.

"Once he realises he's on to a potential target child, then he starts asking questions about who uses the computer and telling her not to save copies.

"It's typical grooming, luring and entrapping of a child".

The investigator spoke to the man on the phone

Soon the man wanted to exchange text messages by mobile phone and even spoke to our undercover investigator, still believing he was talking to a schoolgirl.

Eventually after liaising with Sussex police, we agreed to meet him.

He insisted on choosing an isolated location on the south coast - a spot where he could see our girl coming and establish she was alone.

He repeatedly told Sydney not to inform friends or relatives.

What he did not know is we would be filming the encounter with hidden cameras.

Danger

When he finally showed himself his first words were " you look sexy".

Immediately he tried to get her onto his motorbike.

Marie-Louise did her best to keep him talking but he became insistent that she got on his bike.

He was no longer interested in chat - only in persuading a 14-year-old child to go away with him.

O'Connell: paedophiles try and cover their tracks

At that point Marie-Louise signalled she felt in danger and the cameraman and I moved in to question the man about his intentions.

Initially he denied everything and tried to leave.

As we followed making clear we had seen all his conversations on the internet, he tried to pretend he was just trying to protect the girl from 'dodgy people on the internet'.

He admitted what he had done was wrong and promised never to try and approach children on the net again.

As he left on his motorbike he was pulled over and arrested by officers from Sussex police.

Menace

They took him into custody, searched his home and confiscated his computer hard drive.

He was later released without charge.

As the law stands there is little the police can do until someone commits an actual physical assault.

The government has promised to introduce new legislation that will create a new offence of 'grooming' children for sex.

Until then their only protection remains their parents' vigilance.

Our investigation suggests the dangers are real and the adults who stalk the internet looking for children are not merely virtual reality fantasists but a genuine physical menace.