Doctor Who star Matt Smith once put his grandfather in charge of his fan mail and was stunned when his elderly relative replied to a steamy request for sex.

The British actor normally asks his mother to sort through the piles of letters he receives, but his grandpa once volunteered to lend a helping hand - and got more than he bargained for.

Smith tells Britain's The Times Magazine, "The first letter he ever opened... was what he described as 'very blue'. But he has a wonderful sense of humour, my granddad. So he get this letter and it opens with, 'I want to...' you know... Well, you know, there was sucking and... and all that stuff involved. It was pretty graphic. But anyway, she (the fan who wrote the letter) was about 40 or 50 and asked me to go to her house in Essex (in England), I think it was, and you know, 'take care' of all these things that she was describing.

"My granddad wrote back, 'Matt isn't available but I'm his granddad and I am.'"