Zohra Sehgal
From Tardis Wiki, the free Doctor Who reference
Zohra Sehgal (born 27 April 1912) played Sheyrah in the Doctor Who story The Crusade. As of 2012, she is the oldest living Doctor Who actor. If she lives to 27 April 2012, she will become the first person associated with Doctor Who to reach the age of 100.