IT was a fling with a sting. He is one of Britain’s most popular composers of film scores and contemporary classical music. She is a soap actress, 25 years his junior who has had roles in Casualty, The Bill and, from next week, will appear in Coronation Street.

During the summer Michael Nyman, best known for the soundtracks of movies such as The Piano, and The Cook, The Thief, His Wife and Her Lover, embarked on an affair with Jane Slavin.

Their relationship was sparked by an encounter online - and, when the affair began to sour, she plotted to gain her revenge via a honeytrap on the internet.

Slavin, in her late thirties, created an alter ego called Lucia on Facebook, the social networking website, with the intention of seducing Nyman anew.

After a passionate exchange of messages over a few weeks, Nyman was duped into rushing back from a business trip to China to meet “Lucia” at a cafe in Crouch End, north London. Slavin turned up to humiliate Nyman in person - by revealing that Lucia was a hoax.

Some weeks earlier Slavin, who has auburn hair and brown eyes, had established Lucia Keenan on Facebook with an alluring fake picture.

She then began to flatter Nyman in her messages, saying that she was a huge fan of The Piano - for which he gained an Oscar nomination - and Brief Encounter.

Nyman, who cuts a Philip Larkin-esque figure with balding head, horn-rimmed glasses and squat frame, may look like an unlikely seduction target, but he fell for it. He embarked on an e-mail exchange with Lucia, becoming so obsessed, it seems, that on one day he sent her more than 100 explicit messages from a hotel room in China.

This weekend Slavin explained why she felt compelled to embarrass her former lover in such a public way - and admitted to ulterior motives.

“I wanted to get my own back,” she said this weekend. “I had been having an affair with Michael but was feeling increasingly unhappy. I was also fed up with what I considered his meanness and felt I was possibly not the only woman in his life.” She admitted that she had spotted the potential for extracting a publishing deal out of the story.

They first met at the Festival Hall in London in the summer and, according to Slavin, many of their dates were at concerts where “Michael got free tickets”.

After several weeks the affair began to peter out. “I was very upset and so thought up this revenge,” said Slavin.

Since mid-December Slavin has been writing her own blog, The Facebook Diaries, which relate her affair with an unidentified man known only as “Maestro” - but based on Nyman.

So far she has written five blogs, which Nyman failed to detect because she devised a way of blocking access if he used his normal computer addresses.

Lucia’s blogs are part-fact, part-fiction. Her plan had been to write another 20 over the next few weeks and then secure a book contract. The finale was to be the revelation of how Nyman fell into the honey-trap.

Following their messaging, “Lucia” had arranged to meet Nyman at the cafe, not far from Slavin’s home. He went in the hope, no doubt, that their electronic relationship would blossom. Nyman arrived at the cafe and waited for Lucia.

After a while Slavin arrived, as if by coincidence. “Fancy seeing you here,” she said. “I haven’t heard from you for a while.”

Nyman, who also composed the soundtrack for The End of the Affair - in which a middle-aged man is deceived - was thrown. He muttered about being there to meet a contact. Slavin then asked if she could sit down. Then she delivered a bombshell. She said that she was Lucia and had brought the passionate print-outs to prove it.

The Lucia blogs were written after that encounter. Although she describes Maestro as “very handsome” after her first date, she also says he was “not much bigger than Ronnie Corbett”, which is a mite unfair as Nyman is just under average height.

In other blogs she comments on the “hair in his ears”, “his swollen ankles” (apparently he has a medical condition) and “the dandruff, unusual for a man who is bald”. There are also descriptions of how Maestro fell asleep rather a lot and some embarrassing revelations about his private parts.

Lucia relates stories about his alleged meanness, such as coming back in a taxi from central London when he paid only his half of the fare to his house. Lucia was left to pay the rest - as was Jane in real life. She did not have enough money and was fortunate that the driver took her home without charging.

“I’m not saying anything,” Nyman said this weekend. “Nor will I attempt to read what she has apparently written. I’d much rather talk about my music.”

Nine years ago Slavin brought out a romantic novel, Writing on the Water. One reviewer thought it probably autobiographical and called it “utterly heartbreaking. Thank you, Jane, for every word”. Nyman is unlikely to be grateful for any sequel.