Diana Rigg: It hasn't always gone swimmingly I end up meeting Diana Rigg - Dame Diana since 1994 - not once but twice to explore the subject of her debut on Doctor Who, which for a single episode might sound a touch ridiculous, almost obsessive. It's just that for one reason and another, it takes slightly longer than usual to figure her out. The first time round, we both get frozen into attitudes of polite formality thanks to a combination of the winter cold and the plushness of the central London hotel suite we're in. Besides that, her actress daughter, Rachael Stirling, with whom she co-stars in this episode written specially for the pair by Mark Gatiss (of League of Gentlemen fame and much else besides), has decided not to join her mother for the chat. Rigg is sanguine about her daughter's no-show - "Like all mothers, I don't ask questions," she purrs, giving me an amused conspiratorial look as she orders a decaf cappuccino and a round of grilled Gruyère on toast. A star of the British stage and a Sixties screen legend as a result of those female-empowering roles of Emma Peel in The Avengers and James Bond's one and only wife in On Her Majesty's Secret Service, Rigg has more than enough to say on her own account. And yet the absence of Stirling - her only child, by her second husband Archibald, whom she divorced in 1990 - hangs in the air, making it hard to read her offhand, if amicable, responses. The Doctor Who episode, The Crimson Horror, in which Rigg, 74, plays a wicked, religious-maniac Victorian mill-owner called Winifred Gillyflower, lording it over Stirling, 35, as her blind daughter Ada - is the fruit of a generation-spanning friendship. Gatiss and Rigg got along famously during a 2007 run at the Old Vic of All About My Mother - he playing a transvestite, she a lesbian diva. Last year, appearing with Stirling in a hit revival of The Recruiting Officer, Gatiss chatted with her about his Whovian idea during their mid-show walkabouts - "We got so engrossed we almost forgot to come on," he recalls. That mother and daughter signed up swiftly and had a whale of a time filming their first screen venture together, is not in doubt. "Much laughter," Rigg offers succinctly. Gillyflower is the latest in a line of monstrous mother figures for Rigg, who was born in Doncaster in 1938. The roll-call includes the insanely possessive anti-heroine of the television series Mother Love, her acclaimed Medea, and the sinister Mrs Venable in Tennessee Williams's Suddenly Last Summer. Her newly introduced character on Game of Thrones - the acidly amusing Lady Olenna Redwyne fits the pattern - "another harridan, very strong and rather splendid in that she talks about sex openly." She doesn't seek out gorgons, she says, but doesn't spurn them. An awful lot of actors shy away from the uglier aspects of the human condition. They want to be liked which is a cop-out. You've got to go for it," she says. Does it bring to the fore issues as to whether she has been a good parent herself? You don't ask those questions. I only know how to play bad mums because they're the best parts. What emerges more fully when we meet again a few weeks later, near her Fulham home - the air still biting cold but Rigg more relaxed and talkative - is that work matters less to her these days. Yes, she's delighted when a job comes along - "I'm up for anything" - but in itself it's not enough. She treasured the brief time in Dubrovnik filming Game of Thrones because of the beautiful location. While she helped change television's landscape with The Avengers - "There were no prototypes for me - the telly was full of little blonde juveniles" - now she yearns to see more of the world while there's time. "I've never seen myself as just an actor," she says, enthusing about a trip to Bhutan: "It's got weed by the roadside - you can dry it, take it home and smoke it. If I had my way I'd spend the rest of my life doing that! She's happy to chew the fat about The Avengers ("We had no idea it would be defining, it was nose to the grindstone - working all hours that God gave") and compare it with the technical advances of Doctor Who: "I love the fact that we had to make-do - pretend [the danger] was around the corner instead of presenting it on the screen." But she's happier still to skip to other topics - including, relations between the sexes: "I think guys have a very difficult time these days. The point is to have fun together. Does she have regrets? Not really. I'd love to have done more film but you can't have everything. I've had my moments of finding a pound in the old handbag which I didn't know I had - very good for you they are too those moments. It hasn't always gone swimmingly but overall I've had so much it's greedy to want more. The secret of her success? Down in part, she reckons to no-nonsense Yorkshire ways - plain-speaking and not fussing too much about what others think. "You go your own way - you think, "That's what I want to do, it gives me pleasure" - the rest of the world can swing on by." If Stirling has inherited something of that attitude, which her refusal to play ball publicity-wise suggests she has, then good on her, and on her ma too. Doctor Who: The Crimson Horror is on BBC One on Saturday 4 May at 6.30pm