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Pity David Tennant, filming the Dr Who Christmas special in 30C heat. What tricks does the film trade have to make summer seem like winter, and vice versa?
Festive filming in sunny Cardiff
On a mid-summer's day, few are those who venture out suited and booted. But that's what Time Lord David Tennant and co-star Catherine Tate, in full meringue, have done this week while filming the Dr Who Christmas special.
Producers decked Cardiff shopping centre with giant snowmen and Christmas trees as the city's temperatures nudged 30C.
Extras milled about in scarves and woolly coats as shoppers in sunglasses looked on in sympathy. Asked by fans how he was coping, the Time Lord shouted back, "It's blinking boiling."
"Filming winter in summer, that's really difficult because people overheat so quickly," says freelance drama producer Matthew Bird, currently filming New Street Law with Red Production Company for the BBC.
"I last had to do the opposite - film a barbeque in February for ITV's Jane Hall. It was really quite tricky. Getting hold of a barbeque and other summery props was not impossible, but it was a matter of keeping everyone warm.
"It wasn't so difficult during the day but we were filming until 1am. So lots of space heaters, and people ducking inside between takes. The cast had to suck on ice cubes to cool their mouths down so their breath wouldn't condense in the cold air."
The episode in question screened last Wednesday, and he's confident the team pulled it off. "It looked like summer."
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And in the venerable crime series Midsomer Murders - which despite the name and the idyllic summer setting is filmed in winter - John Nettles and Daniel Casey wear thermal underwear under their lightweight suits so they don't shiver.
Freelance producer Simon Mills, in his 17 years in the business, has worked on many an out-of-season set.
"If it's summer, filming at night avoids the problem of each scene being in blazing sunshine. Although, with sunset so late, you have to work quite long days. If you do film during the day, there's the problem of the actors peering into the sun. We screen the area with a silk - much like a stretched-out parachute - to diffuse the sunlight.
"The sun can play havoc with continuity. It's not so bad in the United States, as you can be relatively confident it will stay out, but in the UK, a cloud might come over between one take and the next."
Any weather effect can be recreated
But to make a summery location seem well and truly Christmassy, it's time to call in a special effects company to provide a blanket of fake snow.
"Falling snow may be made from chemicals or ash - they might burn something, as ash looks like snowflakes. For fallen snow they use finely shredded paper or sometimes salt - as it dissolves in water it's an easier clean-up job. But you have to film quite tight, so as not to get rich verdant greenery in shot."
There are tales - "perhaps not entirely apocryphal" - of crew spending several days picking leaves off trees.
"Rarely is filming simply a matter of turning up and pointing a camera at something," says Mr Mills.