It's a different feeling, being back for a second series, says Steven: "Last time nobody knew about us and there was some scepticism about 'modernising' Sherlock Holmes. And now look at Benedict and Martin, they are so famous in those roles! So far the series has sold in over 180 countries worldwide, so it's a very big change."
The big challenge in that case has to be - how do you follow such a success?
"Well this year, knowing we were a huge hit, I suppose we felt let's do the three big things, The Woman, the Hound and the Fall."
"Instead of making people wait years and years, we thought - to hell with deferred pleasure, let's just do it now, more, sooner, faster!"
"That also means we see three different sides to Sherlock. We have Sherlock and love, Sherlock and fear and Sherlock and death. He definitely goes through the mill in this new series."
Steven who fell in love with Conan Doyle's Sherlock Holmes books as a child says he and co-creator Mark Gatiss are the biggest Sherlock Homes fans.
"We are the biggest Sherlock Holmes geeks in the world. This has become such an enormous international hit, it's sort of preposterous, it's like our vanity project, it's our hobby. And yet everybody has joined in!"
In response to suggestions that there should have been more than three episodes, Steven says:
"We think of them as films because they are ninety minutes long and once we knew we weren't doing hour long episodes they needed to be on that sort of scale. They have to have the size and weight of a movie."
As to how he feels the two series compare, Steven explains
"I think the first series was more about John Watson being redeemed from being a massively traumatised war veteran into a bit of a hero. This year it's more about the forging of the mighty Sherlock Holmes."
And as to what it is that make the stories so enduring, Steven adds
"We've almost forgotten how good the characters of these stories are. They're not just an old artefact that has become, by accident, venerated. They are in my opinion, without a doubt, the biggest hit in fiction, since their launch over a 100 years ago in the Strand Magazine, it's now a hit movie series and a hit television series right now and its down to the characters who are perfect, they are brilliant."