The woman, who had been working as a trainee solicitor at the practice in London for three months, told a disciplinary tribunal that the partner sang a song that referred to her vagina, describing it as “lovely”, despite claims that she had encouraged him to “say something outrageous”.

The tribunal found that the partner had behaved obscenely and had been motivated to do so by the encouragement of the woman, referred to as Person A.

It also noted that the woman did not make a formal complaint about the partner until 18 months later – after she was overlooked for the role of newly qualified solicitor – and that after the party she sent the partner drunk emails inviting him for drinks.

The woman said she delayed reporting the incident because she felt vulnerable as a trainee. She told the hearing that she was “shocked and humiliated to be spoken to in such a degrading fashion”.

The partner was fined £23,000 for misconduct and ordered to pay £22,800 in costs. An anonymity order was granted to the partner on the grounds of his health.

The tribunal accepted that the partner had apologised to Person A and that he was “extremely embarrassed” by the incident, which was filmed.

It ruled that his behaviour was “a grave breach of his position of trust” given the public nature of the event, his status as a partner, and the presence of his colleagues.