Pee-for-all

During a recent visit to Herbert Smith's London office, one of Tulkinghorn's female colleagues was a little shocked to discover that in addition to the ladies' and gents' lavatories in the firm's client dining area, it also has one for unisex use. Mrs Tulkinghorn was a little puzzled as to why such a room existed, especially after being told that she was only allowed to enter if accompanied by a member of the opposite sex. Please send explanations, in confidence naturally, to the usual address.