A spokesman said the incident took place around 6.40pm on Wednesday, December 3 (2014) as the victim exited the London Underground ticket barriers and was making her way to the mainline station.

Detective Constable Suleman Yazdani said she noticed a man walking towards her from the other direction, and stepped towards the wall to avoid him..

The officer is encouraging other victims of unwanted sexual behaviour on the Tube or railway to report it to staff or officers as the victim did in this case.

After BTP released the image of the man today DC Yazdani added: “I believe the man in the image we have issued today can help us with our investigation into the assault. Who is he?”

Anyone with information is asked to contact British Transport Police on 0800 40 50 40, or text 61016, quoting reference TSUB/B10 of 05/01/2015, or call Crimestoppers anonymously on 0800 555 111

If the dimwits from the British Transport Police had bothered for 30 seconds even to view the video from the CCTV cameras, they could easily have concluded (as did everyone else who subsequently viewed it) that the woman was a liar.

But it probably suited their purposes to have a bit of fun, to issue a press release, to appear to be acting in the public interest. And of course to make themselves feel important.

No one is safe from prosecutors' terrifying incompetence on 'sex crimes'

The case of Mark Pearson, accused of sexual assualt in a crowded London station, is another terrible error by the Crown Prosecution Service

Julia Hartley-Brewer

The Crown Prosecution Service has taken leave of its senses. That is no longer beyond all reasonable doubt.

More and more people are now asking if the body charged with prosecuting offenders for their crimes is up to the job following the latest debacle over innocent men falsely accused of sexual assault.

This latest failure is not about the high profile cases involving former Cabinet Ministers, senior military men and celebrities whose lives and reputations are trashed in public but who at least have the opportunity to fight back in the media spotlight.

This is about the far more sinister cases that don’t make the front pages. This is about the men who aren’t rich and famous enough to get to tell their side of the story except to a jury.

It is a 21st century cautionary tale because what happened to him could happen to anyone at any time.

The man in question is Mark Pearson, a 51-year-old artist and cabinet maker. We know who he is, his age, his occupation and the town where he lives. We even know what he looks like.

We know all this because Mark Pearson was accused of sexually assaulting a woman at Waterloo train station on his commute home from work. This made him an alleged sex offender and we all know what that means, don’t we, nudge, nudge? No smoke without fire, eh?

His alleged victim, who cannot be named for legal reasons, is apparently a famous, award-winning actress in her sixties. But her name will never be in the public domain unless she so chooses. Lucky her.

The actress told the police and the CPS that, during an evening rush hour at Waterloo station in December 2014, a man later identified as Mr Pearson came up to her, smashed down on her shoulder and then pushed his hand up her dress and sexually assaulted her with this fingers before running away when she shouted for help.

A shocking accusation, I think we can all agree. And certainly one that the police should take seriously and investigate to the full extent of their abilities.

Which is precisely what they did, checking the CCTV cameras at the station to identify a bald man carrying a bag on his shoulder and a newspaper in his hand walking through the station and passing the alleged assault victim.

The only problem was that the CCTV footage showed no assault at all. On the contrary, it showed Mark Pearson walking through the station minding his own business, his hands clearly visible at all times, the right one clutching his shoulder bag strap, his left hand – the one he is supposed to have thrust up the actress’s dress – clearly holding a newspaper.

He did pass by the alleged victim but – as the footage makes abundantly clear – only for a split second. He also did not break his stride or start running, as she claimed.

There were no witnesses, no forensic evidence and his accuser also failed to pick Mr Pearson out in a police line-up.

At this point in the investigation, what would you have done? Yes, exactly.

It was blatantly clear at this point that either the police had got the wrong man or that the alleged victim was wrong, confused or just plain lying about the assault.

Yet, without a single shred of evidence, the police decided to charge Mr Pearson with a serious sexual assault and the Crown Prosecution Service took the case to court.

Thus began what Mr Pearson has called a year-long "Kafkaesque nightmare" to clear his name.

Not surprisingly, after the ordeal of a three day trial, the jury at Blackfriars Crown Court took just 90 minutes to clear Mr Pearson of the charge of “sexual assault by penetration”. Indeed, you have to wonder why they needed more than five minutes to come to that conclusion.

As Mr Pearson told the court: “I would have had to crouch down, put my hand up the woman’s skirt... penetrate her, take my hand out again... all while holding the newspaper and walking along the concourse. It’s preposterous. I did nothing. One of the many frightening aspects is that this could have happened to anyone.”

The CPS, in mind-boggling defiance, continues to insist there was “sufficient evidence” for this case to go to trial despite all the evidence to the contrary.

There is undoubtedly enormous political pressure on the CPS to bring more prosecutions against sex offenders, and specifically more successful prosecutions. Yet, despite more than 5,000 extra rape prosecutions being brought in 2014, the CPS won only 77 extra convictions.

Again and again we hear of cases coming to court on the flimsiest of grounds when anyone, after a cursory glance at the facts, could see there would be no chance of conviction.

The Director of Public Prosecutions, Alison Saunders, must realise that she is not doing sexual assault victims any favours by bringing cases like Mr Pearson’s to court.

Victims of rape and sexual assault want sex attackers to be brought to justice, not the pointless persecution of innocent men who just happen to be in the wrong place at the wrong time.

The question must be asked: is the CPS still fit for purpose?

Even on its own absurdly low threshold for evidence, it is abundantly clear that the Crown Prosecution Service is guilty as charged.