Gareth Neame is the British Emmy and Golden Globe award-winning producer behind Downton Abbey - the man who originally proposed the idea for the drama to writer Julian Fellowes. Katie Jarvis asked him a little more about the acclaimed new film

Gareth, it must have been such fun seeing the cast back together after several years apart.

I think we all felt the same [delight]… but they weren't the ones who had had to make it all happen! It had taken me about three years to get everyone together again. I can't think of any other film that's got 20 leads in it - it's unbelievable even for a TV show - and it only took for one of them not to be available in the window of opportunity that we had. Would we get Hugh [Bonneville]? Would we get Maggie [Smith]? So when I saw them all assembled, I thought: Phew! We've done it!

The film revolves around a very important visit: the King and Queen are coming to Downton! What a fab storyline.

We've done some really big set-pieces in the TV series so it was important to try and do something even bigger for the film. On television, there were multiple intertwining storylines: you'd have a comic story doing this; and then you'd have a sad story - Edith not being able to have her daughter, for example. All these different things going on. You can't do that with a film: you need everyone to be embroiled in one shared endeavour. Not only did [the royal-visit storyline] raise the stakes, giving us the lavish production value and costuming that everyone expects; but, from a story point of view, it meant all of the characters were focused on the same result.

As you say, there are incredibly lavish and luscious scenes - including more than 100 members of the current King's Troop Royal Horse Artillery taking part. How did you manage that!

That wasn't easy - I don't think they've ever participated in a piece of fiction before. If we'd been brand new, it perhaps would have been harder; but because Downton is known to be such a good calling card for British culture, heritage, and so on, there was a willingness to make that work. They really enjoyed the few days of filming and we liked working with them. There were around 120 troopers and 80 or 90 horses, so we had to create a whole temporary stable-yard in a field, with huge marquees for the troops to sleep in.

Alastair Bruce is Downton's historical advisor. What sorts of details has he alerted you to?

One of the most interesting is bear-hugging - this male thing. So, for example, when Hugh Bonneville [Earl of Grantham] bonded with Matthew Crawley after Matthew provided an injection of money that was needed, they had a great scene together. As Hugh said, the instinct - when someone saves your life like that - would be to hug each other. Well, Alastair said, 'Absolutely no way! I may allow you to shake hands over this but all of that other stuff has to go!'

So let's talk about characters. Who could you not bear to be stuck in a lift with?

I guess they did have lifts by 1927! I don't feel like there's any I wouldn't want to be stuck with. If this is a roundabout way of asking who my favourite character is, then I love them all; but I do ultimately think Mary is at the heart of it. She is difficult to get to know; she's a snob; she's opinionated; she's unkind; she's ungrateful. But she's also incredibly loving and she's passionate and she's determined. Out of anyone in that group, you would want her on your side. Certainly, there are 20 leading characters but, for me, she's a first among equals.

Did you mourn the TV series coming to an end? Is there a sense of loss when things you've worked on for so long finish?

I suppose so, although I have never stopped working on Downton. Every single day, somebody is creating something - some product, some branding, some piece of merchandising - so I don't think it's ever going to leave me. But I love the world that we created, and we've been able to tell stories about Britain that I don't feel could have been told in any other way. That wonderful episode where Lady Rose was presented as a debutante to the King and Queen. That's not a standalone story but, if you put it in the context of Downton and characters that you love, it's a wonderful episode. Or the episode where we had a village cricket match: an iconic English thing. Put Downton characters in there and it comes to life. Or motor-racing or horseracing; grouse shooting or fishing or deerstalking: all these country pursuits fitted into the world that we created.

Same question I've put to Julian - is there a future for Downton Abbey beyond the film?

Well, we all enjoy doing it! We finished the TV show a little bit earlier than people wanted - we certainly could have gone on for another season and more; but it was pretty hard holding all these people together. Also, Julian and I did not want to outstay our welcome. We sweetened the pill by very quickly saying that we did have an ambition to make a film. And I felt it was absolutely my duty to get that film made; if we hadn't got there, I would have let fans down. This is supposedly the big screen swansong. However… if it does really well and people go and see it, then I wouldn't rule out us doing another one.