Jessica Martin
From Tardis Wiki, the free Doctor Who reference
Jessica Martin (born 25 August 1962[1]) played Mags in The Greatest Show in the Galaxy and provided the voice of Queen Elizabeth II in Voyage of the Damned. She also voiced Mags and several other characters in the Big Finish Doctor Who audio stories.
She also contributed to the charity reference book Behind the Sofa: Celebrity Memories of Doctor Who.