The royal marriage suffers a major rift in Victoria series three

Having seen off previous interferences, it’s Victoria’s meddlesome sister Feodora which piles the pressure on the pair when she comes to visit the palace, causing friction between Victoria and her husband.

Jenna Coleman, who plays the young queen, told RadioTimes.com and other journalists at the Victoria series 3 press day that it’s by far the “rockiest” the pair have ever been.

“Feodora weaves a plan, and Victoria and Albert become more disparate and can’t really find their way back to each other,” she said.

“I’d say it’s the rockiest part of their marriage, for sure. We push it to the ends with Albert telling Victoria this is his duty, it becomes so disparate. They lose each other for a while.”

It’s Feodora’s close relationship with Albert that Coleman describes as “driving a wedge” between Victoria and her husband.

“Albert really likes her,” said Tom Hughes, who plays the Prince. “Theodora is very smart the way she plays Albert and I don’t think Albert’s ever been played in that way before.

“He sees Feodora as his intellectual equal. There’s a respect for her, but Theodora’s there to play with him and push his buttons.

“She gets him instantly and plays with him for the whole series.”

Dastardly Feodora is a character rarely explored in dramas, with writer Daisy Goodwin instantly leaping upon the character after doing more research into her background.

“I realised that she’s kind of the relation that no-one ever sees,” she said. “Feodora is ten years older than Victoria, and she first caught the eye of George the 4th. The moment that Victoria’s mother saw that she whisked her off to marry the first penniless chap or prince they could find because they didn’t want anything to interfere with Victoria becoming queen.

“So it’s kind of a great moment, and she’s kind of resented her since.”

Coleman agrees. “When Feodora arrives back there’s this unexplored tension between them, a resentment,” she said. “They’re sisters, they love each other and are jealous of each other.”

“Playing out of this story, which is true, is one of the great engines of the plot of this series,” added Goodwin. “I really enjoyed writing it. She’s a fantastic character.”

Feodora’s manipulative game-planning is further enhanced by newcomer Kate Fleetwood in the role – Goodwin’s immediate first choice of actor for the character.

“She is the most amazing actress – I saw her in something and as I was writing Feodora I was so hoping she’d do it,” she said.

“She’s flamboyant. She’s a villain, a wonderful villain and you don’t know how much of a villain she is. She’s the drip of poison in the royal household. That was very fun, I love doing that. She’s great.”

Aside from Feodora, Victoria and Albert face further pressure when Victoria discovers she is expecting once more – causing her to “withhold sex” from her husband as she tires of being perpetually pregnant.

“They’re linked by sex but they stop sleeping with each other,” Goodwin explained. “There’s a really big rift and it’s quite intense in that sense. There’s pressures of being the most famous couple in the world and having loads of children, and also wanted to fulfil their expected roles.

“Are they still the same people when they got married? It’s really interesting trying to view this marriage from the other side.”

The heartbreak doesn’t stop there for Victoria and Albert, with Goodwin promising “terrible sadness” for the pair towards the end of the third series.

“You will all be crying,” she promised. “If you’re not sobbing your heart out…"

Victoria series 3 launches on ITV later this month