Trident female tick
When BA was formed BEA inherited a cambrian captain who was a tranny and was transitioning to a female so perhaps she counts.
I checked in behind they on the T1/T2 fsdo desk behind PB..they had a page boy haircut..a trouser suit and wore a bra under their uniform white shirt (black iirc).
I never flew with PB but a friend did and said they were a competent operator most of the time ..everything appeared normal until the crew turned up for a midnight swim, a comparatively somber affair as they weren't naked. Captain appeared wearing a pokka dot bikini.
Eventually their services were dispensed with after a sim check...