Where is Our Girl's new series filmed?

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"You know what, you just get on with it. I actually didn’t think about home when I was out there because it was such a long time when I was working I couldn’t think about home because I was homesick. When I was out there, I thought 'this is what I need to do', afterwards that’s when I can go home and get all my home comforts that I want. But until now I need to focus and do my job."

Still, the filming schedule sounds pretty gruelling...

"We were filming six-day weeks sometimes," Keegan recalls. "Every other week was a six-day week so we only had Sundays off – so on Sunday morning you knew you were working the next day. There wasn’t much downtime."

And there wasn't much time off in between episodes, either. "I remember when Luke [Pasqualino, who played Elvis Harte] went, he did his last scene and we were already onto the next episode the next morning so we had no time to digest what had happened and move on. There are so many people working on the production and so much to get in, you had to stay on the wheel and carry on working.

As for conditions, South Africa – where much of the last three series were filmed – was pretty changeable. "It was freezing in the morning – we used to wear coats and long johns, loads of layers – but then it got to 10 o'clock when the sun came up and you were literally stripping off. It was one extreme to the other."

Whereas Malaysia sounds on a whole other level: "that was sometimes unbearable," says Keegan. "That was like a really humid heat so you were just sweating the whole time and it’s weird because you just adapt. I used to send my mum pictures with sweat dripping off my nose and she was like 'I don’t know how you do it' and I was like 'it’s the norm now, it’s fine'. As long as you keep hydrated – we had people there constantly looking after us, putting us in the shade. It was quite tough but your body acclimatises."

Keegan even acclimatised to the creepy crawlies...

"I look back now and think I can’t believe I did that. We had to wear leech socks because there were so many leeches and all the crew because they wore shorts were getting bitten by leeches all the time.

"We were staying at a jungle called Taman Negara and we had to live there for ten days – we had to go to work on a boat, that’s how in the middle of the jungle it was, and I remember I ate an Oreo in bed. Big mistake. I didn’t even drop any crumbs, but I came back home the next day and got into bed and you know when something isn’t right? I turned the light on, moved the quilt and there were tiny little brown ants everywhere all over the bed. But you just wipe them off and get back into bed – it was just the norm. South Africa was fine, I could deal with that, but it was more Malaysia and the jungle. That was horrendous."

Our Girl airs on Tuesdays at 9pm on BBC1