Introduced by George in At Her Majesty's Service as "the Countess Hildegarde of Ample Hall", then "your aunty".

Hildegarde says "my dear child, it's me, your great great aunt" to the Queen of Epic.

Cat says "Hilda who?" And suggests she is the Madame Witch.

The episode description says "When an old cousin visits the Queen, Cat, Jimmy and Henri are certain she's a villain in disguise

See also