The hotel charges more than £500 a night for penthouse suites overlooking the River Thames.
DC Khadra Mallin, from the City of London Police’s Criminal Investigation Department (CID), asked for witnesses to come forward after the fight at 9.50pm on August 21.
“This was a prolonged and violent fight which has no place in the City of London and we do not tolerate this type of behaviour.
“We are conducting a thorough investigation and are asking for the public’s help identify those who were involved and help us to continue to make the City of London a safe place.”
Anyone with information is asked to contact the City of London Police using the form on the public portal or by calling 020 7601 2222 and quoting 0207 601 2999. Alternatively, information can be provided anonymously to the independent charity Crimestoppers on 0800 555 111.