Victoria Wood on the great Mozart heist that inspired Loving Miss Hatto

Yet that is precisely what Wood has been doing over the past three years – writing a script that tells the true story of a wonderfully gentle middle-class caper that left the world of classical music in uproar – and music critics with faces as red as a trumpeter straining for a high note.

Loving Miss Hatto is the tale of Joyce Hatto (played by Francesca Annis), an English classical pianist who died in 2006, aged 77. Hatto’s death was marked by glowing obituaries in several national newspapers. The Telegraph praised her “deeply expressive and profoundly moving interpretations” of Liszt and Chopin, while The Guardian declared her “one of the greatest pianists that Britain has ever produced”.

But they also pointed out the extraordinary trajectory of her career: she enjoyed only lukewarm success early on, but received glittering accolades in her later years when she turned to the recording studio, her stage career having been cut short by cancer.

The only problem was that there was a gaping hole at the centre of the story of the sick pensioner who turned in brilliant performances in the studio at her modest Hertfordshire home. Soon after her death, it emerged that many – perhaps most – solo Joyce Hatto CDs didn’t feature the exclusive work of Joyce Hatto.

Instead, the performances of other pianists, whose work had been copied and “pasted in” by her husband, William Barrington-Coupe (played by Alfred Molina), who owned the record label that distributed her work. It’s possible some “Hatto” recordings contain no authentic Joyce Hatto at all.

The BPI (British Phonographic Industry ) called it the most extraordinary case of music piracy it has seen – and still no one knows how much of the work that was said to have been recorded by Joyce was faked, or whether she was party to the deception.

“It’s a very white-collar crime to rip off Mozart, isn’t it? I mean, it’s very…” Wood smiles and pauses, endowing the next word with as much affection as she can muster, “English”.

We’re talking in a cold, upstairs room in Dublin’s Olympia Theatre. Downstairs, the actors and crew are on the theatre’s stage, recreating the moment when Joyce and Barrington-Coupe first met, in 1953 at London’s Wigmore Hall. Wood is being careful about what she says.

Barrington-Coupe – known as “Barry” – is still alive and so, theoretically, could sue for defamation if he feels Wood has unfairly blackened his character (though, it should be noted, his character was not blemishless before all this – he went to prison for tax fraud some years ago).

“Barrington-Coupe admitted he had made tiny edits in Joyce’s recordings because she was too ill to play without making what he called ‘cries of pain’ due to her cancer,” says Wood. “He said he had taken just a few bars from other people’s recordings, patched up her performance and that she knew nothing about it.

"But if you go by the waveforms of the CDs, there appear to be whole movements that are identical to other recordings, so that doesn’t bear out his account of just taking the odd notes here and there.”

So did Joyce know what was being done in her name? “I don’t see how she could not have known,” says Wood. Meanwhile, no one has ever been able to track down the National Philharmonic-Symphony Orchestra that featured on several Hatto concertos.

“That name is just lots of words that sound like orchestras, isn’t it?” smiles Wood. Nor has the NPSO’s elusive conductor, René Köhler, ever poked his head up to say how much he enjoyed working with Hatto.

Did Wood go to meet “Barry”, who still lives in the house where he did all his digital manipulation? “No, I didn’t want to meet him. It would have cramped my style.”

Her film is not a documentary; it is, she says, “above all, a love story”. This is about a couple starting off with very high hopes and they get bashed about by life,” continues Wood.

“My reading of their story is that Joyce hadn’t been treated well in the early years – a professor at the Royal Academy of Music apparently told her that, as a woman, she’d be better off making roast dinners – and they were disappointed how things had turned out. Either it was good fun to create this career for her, or they felt that she was owed some sort of legacy.”

Surprisingly, “Barry” does not appear to have become wealthy off the back of his dishonesty – and the record companies are not bothering to chase any financial damages from him. The real victims, perhaps, are the music critics.

In 1992, writer Bryce Morrison slated a performance of Rachmaninov’s Piano Concerto No 3 by Yefim Bronfman as “devoid of glamour… He lacks crispness and definition.” Yet, 14 years later, when that same recording was being passed off as one of Joyce Hatto’s works, he wrote: “Stunning… among the finest on record.”

“People invested their emotions in Joyce’s story, and when they listened to the music they were telling themselves a story,” says Wood. “And that’s why people are cross – because they fell for it.”

Wood refuses to be too harsh on Joyce and Barrington-Coupe. “I’m not sitting in judgement on them, though I don’t condone what they did. We all do things that we shouldn’t and we’ve all got our justifications for them."

Loving Miss Hatto is on BBC1 tonight at 8:30pm