As the raunchy TV show about a time-travelling nurse and an ageing highland warrior returns, its stars open up about the vibrant love lives of the over-70s – and respond to criticism of the show’s troubling use of sexual violence

Outlander isn’t a show that can be described in a nutshell. Is it a period drama? Sci-fi? Action? Romance? Caitríona Balfe, who has been the show’s star for eight years, still doesn’t know. “God, yeah,” she puffs. “It sort of defies definition, but that’s part of the appeal.” One thing agreed upon among fans is that, against a dedicated attention to historical detail and endless panoramic shots of Scotland, Balfe’s raunchy relationship with co-star Sam Heughan is the beating heart of the story. Heughan, however, insists it’s not just constant shagging: “When it’s written off as a ‘bodice-ripping drama’ I think, ‘But there’s so much more to it.’”

The adaptation of Diana Gabaldon’s novel series follows the story of second world war nurse Claire, played by Balfe, who is honeymooning with her husband, Frank, when she touches a stone in the Highlands and falls back in time to 18th-century Scotland. There, she falls in love with clansman Jamie, played by Heughan. He affectionately calls her “sassenach” – gaelic for “English outlander”. Together, they travel around the world, encountering and often disrupting historical events, moving back and forth between centuries (only Claire has the gift of time travel), going into battle, saving lives, dealing with witchcraft trials, becoming a power couple and having a lot of sex.