Filming onSherlocks first Christmas Special,The Abominable Bride, took place at the beginning of this year.

The rest was a hotchpotch of rumour, deduction and inference.

Is it any different to normal?

You amend what youre doing very slightly.

Theres less overly casual, modern speech, I suppose.

The sentence structures are a bit more formalised so that, inevitably, makes you speak more properly.

How are you finding the costume?

Its fine, its slightly frustrating because you cant get dressed on your own.

You need help thats why people had butlers I guess.

Thats slightly frustrating but I love the end result, I really love the clothes.

They have said a couple of times since weve been on set that were finally doing it properly!

Were doing a correct version at last.

No-one asks the question anymore about modernSherlock, because everybodys used to it?

No, they dont.

Does the period change the dynamic between your two characters?

It might change it slightly.

Presumably the Victorian era changes Johns relationship with Mary?

Then, you were more likely, I guess, to be a wife and a homemaker.

So Johns attitudes towards Mary havent regressed?

And she might wellnotbe one in this version.

His expectations at the time would be different.

Perhaps hes slightly less likeable than the modern John?

[Deadpan] No, Im very likeable.

Im always likeable at all times.

[Laughter] I dont know.

The idea is obviously not that.

Again, Victorian John was likeable,Diary Of A Nobodysounds like it was written yesterday, to me.

So I dont think its that different.

Essentially, theyre still us.

The Victorian Watson was very much in awe of Holmes.

Thats probably a slight difference between our normal modern one and this one.

Modern Watson definitely thinks his friend is a genius but also anenormouspain in the arse [laughter].

The difference for Victorian would probably be that hes got more patience, I guess.

Are they Holmes and Watson rather than Sherlock and John?

You mind your own business!

[laughter] This feels like Richard Nixons last stand, because weve just been told to say nothing!

Deny everything, Baldrick!

So yes, possibly.

Just because that was one of the idioms of the new series?

Well, Im quite familiar with them now.

As part of your preparation for playing it?

But it does inevitably feed into the general universe of my playing him.

Is it very knowing, subverting what you had before?

Theyre there to be enjoyed without being sent up.

Its still fast-moving, theres no sense of it being sedentary because its old.

Does that show how faithful the other series is, because youve had to change relatively little?

I think thats what so many real Doyle-bods loved about it.

And they could have hated it.Icould have hated it!

There were things that werebeggingto be disliked [laughter].

That seems to be what people mainly respond to.

Mainly, mainly, what has gone over a lot is whatever fortunate things happen between Ben and I.

Is there anything mischievous about doing this when the last series ends on a big cliff hanger?

Im also a big believer in notjustgiving people what they want because, why should you?

There was resistance about series three among die-hard fansdie-hard fans!

You decide to follow them on that journey or not.

I dont think weve lost too many people.

Even the people that were is series three as good?

Has the dynamic with Mary Morstan changed things?

actually, people still really liked it.

People only get angry because theyre still engaged by it.

Theyre absolutely the angriest people, who hate us most, are the…

Ones who watch it over and over…

Mark Chapman, ladies and gentlemen!

He wasnt a Kinks fan, he was a Beatles fan, he wastoo muchof a Beatles fan.

Would you have been interested in joiningSherlockif it was always a period drama?

I would if the writing had still been as good, absolutely I would.

I was resistant to it because it was modern.

Before Id read it, I thought Oh, modern Sherlock Holmes, could that be…you know.

Well, it could clearly be rubbish because most things are rubbish whether theyre modern or old or whatever.

I was resistant to it but I saw how good the writing was.

What have you enjoyed more about the Special compared to making the normal series?

Thats not meant to sound like Im not enjoying it, but nothing more.

Its just an enjoyable show.

Theres a bit of that, because, thank God, were both working.

Weve got our own stuff to do, our own lives and all that.

My family takes up a lot of my life, even when Im not working.

We dont hang out an awful lot, no.

Where doesSherlockfit into your career?

Is it a bit of a touchstone, something you hope you might maintain in the future?

I think so, yeah.

Ive always believed in doing things as long as one wants to do them.

You should at least work fora weekon it.

I think as long as were all free and enjoying it.

I know its a good show, we all know its a good show.

Is spending huge chunks of time away from home something youre trying to avoid?

Kind of, but theres no way round it.

Well thereis I could stop acting, but it would just mean not taking interesting opportunities.

But yeah, I dont massively want to be away all the time, thats true.

Ive got to really want to do something to go away.

John Watson had the moustache in series three, now another in this.

Can fans expect any more facial hair inSherlockseries four?

[Laughs] I dont know.

There seem to be some David Burke and Jeremy Brett parallels with Sherlock and Johns costumes in the Special.

Is that a deliberate nod?

No its not, I think they just got it right, and were getting it right.

Its much more on the books, and images and photographs.

More on that, really.

But that series, they got it right.

I still love watching that.

The Abominable Bride airs on BBC One on the 1stof January.

Come back tomorrow to read the set visit round-table interview with Sherlock creators, Steven Moffat and Mark Gatiss.