In the original stories, Sir Arthur Conan Doyle made little reference to Sherlock Holmes's parents, but in the opening episode of series three of BBC1's Sherlock, co-creators Mark Gatiss and Steven Moffat take the bold step of introducing them.
However, unlike the erudite and highbrow mother and father you might expect to have produced prodigies like Sherlock and his brother Mycroft, Mr and Mrs Holmes appear to be a charmingly ordinary couple.
Gatiss makes the comparison with the Crane family from well-loved US sitcom Fraiser. The two snobbish intellectual brothers, both psychiatrists, had a doting mother and the most down-to-earth father imaginable – a retired cop, never happier than when watching a football game, beer in hand, in his favourite armchair.
"Sherlock and Mycroft are like Niles and Frasier Crane," said Gatiss, speaking at a preview screening of series three opener The Empty Hearse. "They have very ordinary parents, and actually Sherlock is more likely to be the product of a loving home than a broken one in a strange way.
"It’s almost like he was indulged as a kid."
Gatiss, who plays Sherlock's equally gifted brother Mycroft, said it had been important to him and Moffat to push the boundaries of Sherlock Holmes canon in the new series.
“This is really the first time we’ve ever gone beyond [the original stories],” said Gatiss. “I don’t know if Sherlock Holmes’s parents have ever been shown [in a dramatisation] and it felt like the right thing to do in the third season, to be even cheekier. Why not?”
Sherlock: The Sign of Three is at 8:30pm on Sunday 5 January on BBC1