The star of the Second World War epic reveals five secrets from the set

JONAH HAUER-KING WORLD ON FIRE Tomorrow, 9pm, BBC1

1 My character Harry Chase worked as a translator in the British Embassy in Warsaw before becoming a front-line soldier, so I had to learn to speak Polish. I must thank Zofia Wichłacz, who plays Harry’s Polish lover Kasia (pictured, with Harry), for patiently helping me understand Polish over many weeks. It’s a beautiful language and has a musicality to it, but it’s not easy to learn!

2 Harry is from a well-to-do Manchester family and has a wardrobe of fine clothes, including several beautiful suits which were tailored for me. I had my eye on one from the moment I first wore it, a dark blue, three-piece, wintery knit suit, which I’m delighted to say I was allowed to keep.

3 I had to look adept with a pistol because, as an officer, Harry would have carried one. I needed tuition. The first time I held the weapon, my arm was straight and the armourer said, ‘You’re not in an American movie, that’s not what you do, you have to show a bent arm.’ Lesson learned!

4 Much of the filming took place in the Czech Republic, and it was on occasions bitterly cold, as low as -9°C . We’d be marching and there’d be frost on our hair. A proposed parachute jump had to be postponed because the snow was so deep it was too dangerous.

5 There were a lot of sets built. In Lancashire they created a police cell and two nightclubs, while in Prague a square was constructed to represent Warsaw in its pre-war pomp. It was slowly dismantled as Nazi bombing reduced it to rubble. The cafe Kasia waitresses at was there – she served alcohol-free beer instead of the real thing to stop the supporting artists getting merry!

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