Who was the longest british reigning monarch?

Elizabeth II recently celebrated (From the 2nd-4th of June 2012) her 60th Jubilee of her reign. She is still reigning but she began her duties in 1952. Before her, Queen Victoria ruled from 1837- 1900, 63 years. Finally, Elizabeth I ruled from 1558- 1603, 45 years.

So to answer your question, Queen Victoria was the longest reigning British monarch but if Elizabeth rules into 2016, she will be bestowed this title.