Lady Huntingdon was a member of an extinct tiger-like species. Though she seemed frail and elderly as a human, she could kill a human in her tiger form. She was a cruel and selfish woman, killing Rector Adams simply for sport.
Lady Huntingdon came to Earth in the 18th century with her granddaughter, Bella Huntingdon. She obtained an estate and title in England. Every year she would hold a ball, seemingly to find a husband for Bella Huntingdon. In fact, she was trying to find a way to get back to her home planet.
In 1764, Iris Wildthyme and Turner came to the ball, with Iris planning to get Turner to marry Bella and then get the estate in the inheritance. Lady Huntingdon found out about Iris Wildthyme's TARDIS and wanted the TARDIS in exchange, which she refused. Lady Huntingdon went to steal the TARDIS for herself, attacking Turner when he tried to stop her. The Fourth Doctor was able to stop her by doing a particle reversal on a message pod in the TARDIS, pulling her into the pod and trapping her inside forever. (PROSE: Old Flames)