David Walliams has swum the English Channel and the length of the Thames, but his latest charity challenge should be a little easier - he is the new voice of the speaking clock.
The comic, who recently joined the judging panel on Britain's Got Talent, has joined other stars including Kimberley Walsh and Gary Barlow in the bid to raise £1 million for Sport Relief.
David said he was "thrilled" to be taking part, joking he was "relieved to hear" that BT only wanted his voice this time around and not to take him on "another gruelling challenge."
BT will donate 10p to Sport Relief every time someone uses one of its landlines to call the clock from Wednesday until April 9.
The clock has been providing the correct time since July 24, 1936, and is accurate to five thousandths of a second.
Its regular voice is Sarah Mendes da Costa who became its fourth permanent voice after winning a competition in 2007.
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