Then she started getting messages. "Great advice mate but a bit too much information for me," a colleague who worked in the sewers team texted. Another emailed: "Who's the chick in the photo??" When next she saw him, he shook his head in disapproval, she said.

Stephen Znautas, an engineer who worked with Ms Yelda, told the court she was "outstanding" in her ability to build relationships within a predominantly male workforce, and was empathetic and gregarious. But she rang him in tears in late April 2016, concerned the poster would be interpreted in a sexual way and she would lose respect among her colleagues.

"[Mr Znautas] stated that having been associated with manual labourers for a significant part of his career, he could see that [the poster] could be interpreted in a sexual way and could lead, in the worst case, to direct lewd comments, and more likely, to behind-the-back comments," the tribunal said.

Ms Yelda and another colleague individually complained about the poster to management, which took it down and apologised, acknowledging it "unfortunately contains a slogan that could be seen as offensive". But Ms Yelda did not return to work and took legal action against her former employer.

Employees for Vitality Works told the tribunal that lubricating the joints had been a key component of their training since 2010 and never been the subject of mirth. Posters used in previous campaigns that were tendered to court depicted male workers doing stretches beneath the same slogan.