A very passionate affair, muses Cohu

In the RTÉ drama series Charlie, one of Charles Haughey's political colleagues is heard wondering what the boss sees in the woman with whom he is known to be having an affair, Terry Keane. "She practically a Brit," he snarls.

Lucy Cohu, the British actor who plays Surrey-born Keane in the trilogy of feature-length episodes, believes she understands why Haughey was attracted to her. "I think she's a fascinating character and one of the few people who could be very honest with Charlie," she says. "I think they were each other's intellectual match and she could say things to him that no one else could. It appears to have been very passionate between the two of them."

Charlie, written by Colin Teevan, shows the late columnist and fashion journalist calling Haughey (Aidan Gillen) “sweetie” – a pseudonym she used for him in her columns – and cajoling him that if she doesn’t “get the story” from him, then “they’ll make it up” anyway.

Cohu describes Keane as “a formidable character” – indeed, many of the women who were prominent in Irish political and media circles at the time were formidable characters. They had to be, in order to break into such a male-dominated world. “Terry did sort of manage to have her own kingdom,” says Cohu. “I wouldn’t have liked to have been on the wrong side of her.”

In the first episode – which airs on RTÉ One on Sunday – viewers will see some straight-from-the-bottle champagne glugging and cackling, fur-coated guests at a party at Haughey’s Abbeville mansion.

This is contrasted with the newly elected taoiseach delivering his “we are living way beyond our means” address from January 1980. It’s a snapshot of a grotesque sense of entitlement – an “us-and-them” world – at a bleak time for the Irish economy.

“I think they’re all slightly grotesque, aren’t they?” says Cohu. “Money, sex, power, politics. And I think at that time, the Eighties, there were some people who were living lifestyles that were grotesque.” Personality-wise, politicians “seem to be much blander these days”, she adds. “At the time there was Haughey and we had Margaret Thatcher. You don’t get those characters as much now.”

Cohu's acting CV includes Torchwood and Ripper Street for the BBC and a comic turn as marijuana-smoking traveller Niki in The Inbetweeners 2. She is also in the cast of the second series of ITV's acclaimed murder drama Broadchurch, which will be shown here on TV3 from January 5th. She is unable to say much about her role or the plot. "I can't tell you or I'd have to kill you."

There is "definitely, definitely" a sensitivity to playing a real-life person who has living friends and relatives. She once played Princess Margaret in The Queen's Sister, a Channel 4 one-off drama from 2005, which, like Charlie, was produced by the company Touchpaper Television. It is just possible that there were some powerful people tuning into it. "That was quite a scary one to take on," she says.

With Keane, who died in 2008, Cohu was conscious that although she was "great fun to play", it was important to portray her "as a woman not as a caricature". Her suspicion is that Keane would have enjoyed the renewed attention sparked by the broadcast of Charlie. "I do get the feeling that she would find the proceedings going on at the moment extremely amusing . . . Yeah, I think she's having a good old giggle somewhere."