According to the report at BBC News, she had fought a long battle with cancer, and died in hospital in London. As well as appearing in Doctor Who during the Key to Time season, she starred in the movies The Odessa File and The Likely Lads as well as the TV series The Assassination Run and The Murder Game. She also had stints on both EastEnders and Brookside.
Tamm recently recorded a series of new adventures alongside Tom Baker for Big Finish, which will be released early next year. She had previously reprised the role of Romana for various audio adventures.
Reacting to the news, Sixth Doctor Colin Baker tweeted: “Shellshocked to hear Mary Tamm is gone. A funny, caring, talented, lovely and down to earth lady. My heart goes out to Marcus and Lauren.”