Senior Stage Manager Diana Childs has been with Birmingham Royal ballet since it was based in London under the name Sadler's Wells Royal Ballet. She has stage managed every single performance of The Nutcracker since its creation in 1990. We asked her about her role, and some of the work that goes in to the ballet.

While she evidently takes her responsibilities very, very seriously, Diana is constantly careful to point to the work of all the other backstage crew; the stage staff, wardrobe department, those on the fly floor, the electricians and lighting technicians.

'I very much believe that it's always a shared thing between me and Nick [Ware, lighting] and Doug [Nicholson, Head of Scenic Presentation] and all their teams. My role is very much from when the curtain goes up.'

'I'm responsible for making all the lighting and scenery change at the right moments,' she explains carefully, conceding that it's 'a bit like a conductor for the visuals. I Stage Manage The Nutcracker from the prompt desk. For plays and other theatre this spot is used to prompt the actors but for us it's a control desk with monitors. I have a score, and all the cues are written on it to indicate when everything has to happen.

'I wear a headset and I'm connected to key members of the stage staff, electrics and fly floor [the gallery above the stage]. I also have a cue light system with red to get ready and green to go, in case they don't hear me on the radio. So it's a double-cue back up.

'For example, I will have been given a place in the music by the director - in this case Sir Peter Wright – when he wants the curtain to go out. I'll turn on the red lights for the team to stand by for their cue and also give them a verbal stand-by over the radios, then at the right place in the music I'll give a green light and a verbal go for the tabs [curtains] to go out.

'Another example would be Drosselmeyer's pyrotechnic effect. A device is set up upstage of him and detonated from the side of the stage. We have lots of rules and regulations and people watching to keep the dancers safe. I give the cue, and say 'flash, go', and it’s as easy as that, but it has to be right on the music and exactly as Drosselmeyer turns round.

'The operator who presses the button is in the wings near to him, with a second person watching, and if at any point they think that the dancer's cloak is too close or there's any risk whatsoever, they just won't fire the explosion, because it's just not worth hurting somebody.'

Some of the effects are handled directly by Diana herself. 'I have a gun for sound effects during the battle,' she says. It's as real as we're allowed, but has been modified so you can't put real bullets in it. At the allocated point in the music, the soldier flourishes his gun and I fire the gun to make the noise. One year a long time ago some of the crew rigged up a small cup of feathers and hung it from a wire above my head, tipping it up when I fired the gun. I've got my head down concentrating on the score and the next cue, and I fire the shot on cue and all these feathers come drifting down around me!'

Some of the biggest effects in the ballet are actually the most straight forward. One of the most popular is the opening of Act II, where Clara crosses the stage on a flying goose above a cloud of dry ice. While the technology is very simple, Diana reveals that the timing requires a great deal of attention.

'The dancer gets in at the bottom right down on the floor during the interval, and I send her up,' she explains. 'It takes time to strap her in and get her up there and lay all the dry ice underneath her and I've had complaints where the audience has all been in and ready and they've just sat there for five minutes while we’re still setting up. But also I have to be aware of how nervous the ballerina is who's performing the role. Some of them really don't mind, and I can send them up there and they're happy to wait, but some of them get really scared up there, so I send them up at the last possible second so they’re not up there any longer than they need to be.'

'Luckily I've been doing this ballet for quite a long time now, so I've become quite a good judge of when people are nearly ready and I know when the audience are nearly in.'

With the ballet being performed by the Company most Christmases since its creation in 1990, Diana has had plenty of time to hone her judgement. 'I was involved from the first day of the first rehearsal, and I've done every single performance we've done', she states. 'I'd have to check my records for an exact number but it's way over 300.'

The unfortunate by-product of this is that Diana has never seen Birmingham Royal Ballet perform the piece, her only chance to see the production coming when it was performed by a Japanese Company. Through no fault of the Company in question, her experience was not as enjoyable as you might expect.

'We lent [The Nutcracker] to a company in Japan that liked Sir Peter's work very much,' She remembers. 'A handful of us were sent over to teach them how to run it, and once it was finished and on, I watched it and it was the first time I'd seen it. But throughout the whole performance I was thinking about the stage directions and thinking about what should be happening. Because I know the score so well, I just hear my cues and think 'Fly cue one', and 'go', and you can feel yourself wanting to say these instructions. I tried really hard to watch my friends dancing the piece, and to enjoy it, and even went to watch it a second time, but still found myself watching the scenery!'

For those who have seen the ballet, this attention to the scenery is understandable, as it is John MacFarlane's set which provides arguably the most special effects of the performance. Likewise, it also requires the most managing from backstage.

Diana explains the potential for trouble: 'There's a big transformation scene when Clara falls asleep – or is she asleep? – and the room grows. I have to control every single part of that transformation so that everybody knows what they have to do and at what time so that nothing crashes into each other.

'There's a very real risk of that – if one part of the scenery doesn't go out before the fireplace turns round, it can crash, and if the fireplace doesn't turn quickly enough then the scenery coming in from above will hit the top of it.'

Diana must constantly be prepared to think on her feet. 'Sometimes I just have to make a very, very fast decision because sometimes something might go wrong that's never happened before. A tree might have to fly out and every day it flies out perfectly, and suddenly in the middle of a performance it gets caught. And I have to make the call as to what to do about it.'

'One problem, for example, is air conditioning, which is a killer for live theatre. The moment the curtain goes out you've got all this open space and get air currents moving around the stage and auditorium. This means that all of the silk scenery starts to move.

'They're hung only about eight inches apart, so you might have a situation where one gets caught on another. And that's the hardest thing about Nutcracker, because there's so much moving at different time, and all the light is just on the dancers so it's so dark up there, and there can be delays that mean you’re going to miss cues, so you’re constantly making judgement calls. But that's what's so exciting about it.'

The team also have contingencies for a host of worst-case scenarios. 'One thing which we have thought about for example, is what if the motor broke on the goose and it stopped working?' she reveals. 'How would we get it down and would we stop the show? Would I bring the curtain in? Thankfully we have a whole plan for what we'd do, but I'm not going to tell you what it is because I'm hoping it will never happen!'