Martin Freeman will admit that filming Sherlock “wasn’t that much fun” during the final days of his 16-year relationship with co-star Amanda Abbington when he is cast away on Radio 4’s Desert Island Discs on Sunday.

Freeman, 47, said the couple, who announced their split in 2016 and have two children together, have stayed friends for the sake of their former relationship, as well as for the rest of the family. “I wanted to be civil for us, because when you’ve loved someone for that long and they have been such an integral part of your life, what – that is supposed to not count now?” The actor goes on to say he thinks he and Abbington now co-parent “pretty well, really”.

But Freeman reveals that “by the time of the last Sherlock that we’ve done we were sort of in the midst of splitting up”. Until then, making the show, in which they play John and Mary Watson, had been “great”, he said. “I really love working with her.”

Freeman also tells host Lauren Laverne that his chemistry with Benedict Cumberbatch, who plays Sherlock Holmes in the hit BBC show, is “fairly rare”.

Facebook Twitter Pinterest Benedict Cumberbatch as Sherlock Holmes and Freeman as John Watson. Photograph: BBC/Hartswood Films/Colin Hutton

“Probably nothing I’ve done... has resonated with certain parts of the world’s population the same way Sherlock has. It just hit a lot of buttons for people,” he said. Yet the intensity of some of the fans’ reaction can be “challenging”, he said.

“By the time we filmed the last ones there were some fans who were so adamant that John and Sherlock were gay, they knew it. And they knew that Steven (Moffat) and Mark (Gatiss) were going to write an episode where we held hands off into the sunset together. So when that didn’t happen, there was a chunk of people going, ‘This is betrayal’.”

Choosing tracks from Madness, The Clash and Leonard Bernstein among others, Freeman recalls his childhood as the youngest of five. With only three O-levels to his name, he remembers enjoying being distracted by other pupils at school. “It is more fun to be naughty. There is no way round that,” he said.

He chooses scripts, he suspects, when they are “not begging to be liked” and feels the same way about people. He also talks about his acting heroes, Michael Caine and Tom Courtenay, who “didn’t seem to be doing much, but had a bit of nuance about them”.

Freeman’s upcoming sitcom, Breeders, created with Simon Blackwell and Chris Addison, is to be a reaction to the shock of parenthood, he explains. Being a parent, Freeman argues, is “about 47 light years away from not being a parent” and he finds being presented with “my own shortcomings” the most difficult side of having children.