Police had to be called to a function held by Lincolns Inn firm Trowers & Hamlins after a fight broke out between two party-goers.
Officers from City of London Police were called in the early hours of the morning to the private function room at The Brewery, a licensed conference centre in the City where the firm was holding its annual party.
No arrests were made, but the brawlers were warned to keep the peace, said police.
Senior partner Don Jones, who organised the annual get-together of the firm's staff on 13 October, said the fight broke out at the end of the party between a member of the maintenance staff and a guest of another staff member. It is understood that it took several people to pull apart the two combatants.
The Brewery is known in the City for the quality of its beer, which costs £2.10 a pint. A spokeswoman said the firm regularly used its facilities and would not be barred.