A prominent academic has learnt an expensive lesson - don't make defamatory allegations on Twitter unless you've got some evidence to back them up.
Jo Grady is the General Secretary of the University and College Union and two of her tweets have ended up costing her around £11,000 apiece.
The episode, as bizarre as it was avoidable, began with a tweet by another prominent trade unionist, firefighter Paul Embery.
In August last year he had taken a train from London to Norwich with his children and they found themselves sitting near a group of rowdy, drunken women.
Mr Embery asked them to stop swearing, a request that was met with more profanities and the threat of a bottle in his face. He found the guard, who succeeded in getting them to tone down their language - until he left the carriage and the swearing started again.
Mr Embery then tweeted a photograph of the women, hoping that the train operator might take action.
The tweet went viral, no doubt because so many of us have had to endure similar experiences on public transport.
At this point Jo Grady decided to stick her oar in.
For whatever reason, she sided with the drunken louts, going onto Twitter to accuse Mr Embery of being creepy, bullying women, and inventing details about the episode.
None of which she could have known because she wasn't there.
Mr Embery asked her to retract the tweets. At this point the dispute had not yet got out of hand and Dr Grady had been presented with a way to defuse the situation. She decided not to take it, something she is probably now regretting.
Mr Embery warned that he would sue.
Perhaps Dr Grady thought this was bluff. She would have been disabused of this opinion after Mr Embery raised more than £25,000 on the online platform crowdjustice.com.
The High Court in London heard this week that Dr Grady has now agreed to pay Mr Embery substantial damages for her two tweets.
"They portrayed him as a misogynist, a pervert and a liar, when all he was doing was seeking to defend himself, his children and fellow passengers from rowdy and threatening behaviour on public transport," his solicitor Tom Double told the court.
"They contained wild and reckless allegations; all entirely without foundation."
Mr Double went on: "Dr Grady has now agreed to pay Mr Embery substantial damages and legal costs. She has additionally undertaken not to repeat the allegations or similar allegations.
"Mr Embery intends to donate his damages to charity. My Lord, in the circumstances, Mr Embery is prepared to let the matter rest."
After the case Mr Embery said he had no idea what prompted the attack from Dr Grady, though they have previously clashed on Twitter over the trans issue - he opposes the idea that men should be able to declare themselves women and have access to women's spaces, while she supports gender self-identification. They are also on opposite sides of the Brexit divide - he supported Leave, she supported Remain.
"I was absolutely certain that I needed vindication, I could not let her get away with it," Mr Embery said outside court.
"What she tweeted out of the blue was completely untrue, I don't know what her motivation was.
"I'm enormously grateful to people who helped crowdfund my case, the support was overwhelming.
"The case highlights the issue of anti-social behaviour on public transport, I suspect that many of the people who donated money have experienced it."
He said Ms Grady agreed to pay around £12,000 towards his legal costs, plus almost £10,000 in damages which he said he will give to groups defending women's sex-based rights and the integrity of women's sports.
Dr Grady issued a statement saying she had "reluctantly" agreed to pay damages because she didn't have the time or money to fight the case.
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