The Crown newcomer Emma Corrin has received widespread praise for her portrayal of Princess Diana, but it turns out filming the show wasn’t all plain-sailing.

During a new interview with Glamour, Emma revealed that she had to be hospitalised after filming one of series four’s most difficult scenes on location in Spain.

“I’m asthmatic and I had been ill for a while with a bad cough,” she told the magazine.

“I had to film a scene in a freezing-cold swimming pool, with the kids playing William and Harry.

“It was honestly the hardest scene to film because I was genuinely keeping myself alive treading water, and also keeping five-year-old ‘Harry’ alive, as we found out he couldn’t swim!”

Emma recalled that she paid a visit to a hospital for some antibiotics, but ended up not being allowed to leave.

She said: “The doctors gave me an oxygen test and said, ‘We cannot let you go because your oxygen levels are so low,’ so I was hospitalised.

“I remember the nurses, figuring out what I was filming and saying, ‘We know you’re playing Princess Diana, would you like us to put a cardboard bag over your head so no one recognises who you are?’ in broken English!”

Speaking to HuffPost UK in the lead-up to the new series, Emma revealed that season four of The Crown does not shy away from Princess Diana’s personal issues, admitting she found filming scenes of the late royal’s bulimia especially tough.

“I kind of underestimated how hard it would be,” Emma said. “I was like, ‘it’ll just be like crying on screen, you just get into the zone’… but it was not fun. But I felt like it was important, and so I kind of just did it.”

Read Emma’s full interview on Glamour’s website.