Lord Of The Rings star Sir Ian McKellen is bringing a bit of magic to the Speaking Clock.

The actor, who played the wizard Gandalf in the hit fantasy films, will be the voice of the long-running telephone timepiece until Friday March 13 - Comic Relief Red Nose Day.

Until then, BT will donate 10p from each call made to the Speaking Clock from BT landlines, with the money going to the charity.

Sir Ian, whose career also includes roles in the X-Men films and regular performances with the National Theatre and the Royal Shakespeare Company, said: "Red Nose Day is a national institution and I'm delighted to be at last making my debut with Comic Relief. As for the Speaking Clock, I hope everyone will give me a call, if they have the time, so to speak."

The clock has been providing the correct time since July 24 1936, and is accurate to five-thousandths of a second.

Some of the famous voices who have been heard as the Speaking Clock include David Walliams, Chris Moyles and Cheryl Cole, who all took part for charity.