Lieutenant Gay Ellis Page

Gay Ellis, Senior Operative, SHADO Moonbase Operations - Earth's first line of defense against a power threat of extraterrestrial origin.

Gay Ellis is a senior operative assigned to the command of Moonbase, SHADO's first line of defense againt the aliens.

Lieutenant Ellis was played by British actor, Gabrielle Drake.

Credits

A list of Gabrielle Drake's film and TV credits

Many Thanks to Marc Martin for supplying this info.
A list of all the major UFO actors' credits can be viewed at
Marc Martin's UFO Series Home Page.