The latest episode of Sherlock was even more of a family affair than usual after show supremo Steven Moffat's son played the great detective as a schoolboy.

Louis Moffat played the young Sherlock in a few scenes filmed as flashbacks during His Last Vow, which saw Benedict Cumberbatch's Holmes and Martin Freeman's Watson take on Lars Mikkelsen's blackmailer Charles Augustus Magnussen.

The show, which also stars Martin's real-life partner Amanda Abbington as his on-screen wife, also featured another appearance by Benedict's real parents as Sherlock's mother and father.

Steven's wife Sue Vertue is the show's producer and his mother-in-law, Beryl Vertue, is among the executive producers.

It is not the first appearance in the show by Louis - after an earlier series Sue tweeted fans: " Louis Moffat, our son, was Scared Countdown Boy on #Sherlock . Wasn't he BRILLIANT? Or are we just proud parents?"

Speaking after a screening of the episode earlier this week at Bafta's London HQ, Steven said it was a natural move to include a young Sherlock in the show.

He said: "Once you've got the parents in and you've got the sibling rivalry and stuff, people start to think, 'well what was young Sherlock like?' You just want those things, you want to see those things, it's part of updating it."