A female QC admitted to a sleazy romp outside a busy train station with a solicitor – but weeks later claimed she had actually been sexually assaulted.

The woman, who was arrested and thrown in the cells after being caught drunkenly engaging in sexual activity with her knickers round her ankles, initially accepted a caution.

But as a result of her belated sexual assault allegation, she has guaranteed anonymity for life.

The man she has accused is married father-of-three Graeme Stening, 51, a senior lawyer at a private equity firm.

Married City lawyer Graeme Stening (pictured left and right) allegedly had sex with a leading barrister outside one of the busiest London train stations at the peak of rush hour

He denies a charge of outraging public decency by engaging in a broad-daylight sexual act during the evening rush hour outside London’s Waterloo station.

He also denies sexually assaulting the woman – an allegation currently being dealt with by police and the Crown Prosecution Service (CPS), with no decision yet made on whether it will reach court.

Stening’s solicitor Amarjit Bhachu protested at his client’s name being tarnished by ‘false allegations’.

And a source familiar with the case last night claimed the anonymous QC had belatedly cried assault because she was desperate to keep her drunken romp a secret – and did not care how much harm she did to Stening in the process.

The source added that there were plans to report her to the Bar Council – the barristers’ regulatory body – for bringing the profession into disrepute. However, it is understood the QC will argue she was unwell at the time of the incident, and therefore not in a position to properly consent to the caution.

But the source told the Daily Mail: ‘She is undermining the profession by making such an allegation in order to keep secret the disgrace of a night in the cells for public sexual activity.’

Graeme Stening (pictured), 51, and the QC were drinking together before they were accused of engaging in sexual activity in public near Waterloo station in London

The source went on: ‘It all happened last summer when Graeme met this prominent QC for a business lunch – at her suggestion. It turned into a long, boozy afternoon. At around 7pm they were allegedly seen against a wall right outside Waterloo station. She was said to have been against the wall with her knickers round her ankles.

‘Graeme was also said to be exposed, and was said to have been touching her intimately with one hand, and himself with the other. They were both arrested and taken into the cells overnight to sober up.

‘The next morning, at about 10am, Graeme accepted they had a bit of a snog, but denied any wrongdoing, and was then charged with outraging public decency. But she signed a caution, accepting that they had been engaging in sexual activity in the street. It was not full intercourse, but it was a lot more than a snog.

‘They wouldn’t have interviewed her unless she was sober and she had taken legal advice before signing. And she’s a QC.’

The source went on: ‘Then, six weeks later she goes back to the same police officer and says, “I shouldn’t have accepted this caution”.

‘She said she was going to make an application to have the caution quashed, because she shouldn’t have accepted it. She then said she wanted to make a new allegation – saying she couldn’t remember what happened, because she was so drunk, but now thinks he must have sexually assaulted her.

‘Instead of asking her what on earth she was playing at, and why she didn’t say that before accepting the caution, the officer took it up and phoned Graeme – leaving a message with a member of staff at his work. It’s all maximising embarrassment to him. He was told he would be arrested if he didn’t go for a “voluntary” interview about it.’

Stening, who reportedly lives with his wife of 27 years Sian, 50, in a £1.7million detached house in Windlesham, Surrey (pictured), pleaded not guilty to one count of outraging public decency last September 21

The pair were accused of engaging in sexual activity in public near Waterloo station in London

The source continued: ‘Graeme’s wife is standing by him and understands he’s collateral damage from the QC’s determination to keep her name out of it ... There may well be a formal complaint about her to the Bar Council for making this false allegation, which could lead to her being struck off. Options are also open with the police over this being a false allegation.’

As a result of the sexual assault investigation, plans for Stening to be tried on the outraging public decency charge have been delayed from this month until June.

Stening is the senior in-house lawyer at multi-billion-pound venture capitalist firm Doughty Hanson & Co. The company has faced problems since founder Nigel Doughty was found dead in his home gym four years ago.

Stening, who married his wife Sian in 1989 and lives in a £2million home in Windlesham, Surrey, sat stony-faced at a hearing before Camberwell Green magistrates in south London on Thursday where the case was postponed.

Accepting a caution involves formally admitting to have committed a criminal offence and it being held on record, but with no charge.

Attempts to overturn a caution are rare, and routinely rejected by the police.

As the woman involved has been a barrister for years, she might be expected to have some awareness of the law surrounding cautions. She may also have realised that if Stening went on to face prosecution over the incident – as is happening – her name would almost certainly be raised in a public court, along with the fact that she admitted committing a criminal offence herself by accepting a caution.

Stening’s lawyer Mr Bhachu told the Mail last night: ‘My client, a man of impeccable character, has had his name tarnished by false allegations – and where the claimant cannot be named. The allegations will be vigorously defended.’

Concerns have been raised previously about the fact alleged victims of sex crimes have lifetime anonymity – while those accused face public shame even if the claims turn out to be false.

The QC did not respond to requests for comment.