Strike a light, this is strange. Dot Cotton is in her kitchen, sucking on a fag and talking into a tape machine, recording a message for her husband, Jim, who is paralysed and unable to speak after a stroke. The hardest thing, she says in a trembling voice, "is the thought of you being there... but not being there". And suddenly soap life and real life collide in a terrible and truly moving way.
Dot is just a character in the BBC series EastEnders, of course. The scene is from a remarkable episode to be shown on Thursday, in which she is the only character to appear. There has never been a solo show before in British soap history. June Brown, who plays Dot, gives an astonishing performance, with a script that owes a debt not just to Alan Bennett's Talking Heads but also to the Samuel Beckett play Krapp's Last Tape. It is worth seeing, even if you can't stand soaps. But that's not what is strange. And her own brilliance is not the reason Brown wept when she saw a playback of the recording.
She cried because her close friend John Bardon, who plays Jim, has also had a stroke. Like his character, he is semi-paralysed and barely able to speak. For her, the whole episode – and particularly that line – has a dreadful resonance.
"I miss him terribly," says Brown, in a voice like Dot's, only posher. It is unsettling to meet her out of costume on the set where the show is recorded. Dot's drab kitchen is a familiar sight, after 23 years of EastEnders. The details say a lot about the chain-smoking washerwoman of Albert Square: there's a coronation tea caddy, a tin of value Irish stew and the two china mugs she still fills by habit, although Jim is not coming back from his care home. But the fourth wall is missing, replaced by studio lights. And we're not in the East End, this is BBC Elstree, north London. And the woman who is speaking has Dot's face but she is definitely not Dot.
June Brown is much more elegant. Instead of Dot's monstrous purple semi-beehive and pink dressing gown she wears a sleek bob and a pair of chocolate cords, with a gold-embroidered cardie. "It's a terrible thing," she says of the stroke that John Bardon suffered one day last summer. "It could happen to any one of us, at any time. One minute you're doing this," she says, looking around, "the next all the movement and speech you take for granted just goes."
She usually stays with the 68-year-old actor and his wife, Enda, at least one night a week while filming. "He has always been such a big man, dear. Active. Expansive. An actor needs his voice."
Brown is careful to talk about Dot as a separate person, but there are some traits they share. One is an addiction to menthol cigarettes, so we repair to the battered old cabins that the EastEnders stars use as dressing rooms, where she can sit by an open window and puff away. "John is improving all the time," she says. "His mind is fine, but you just long for him to be able to express himself as he could. It's such hard physical work, to recover from a stroke." Can he talk? "Sometimes he will try and a sentence will come out. He is having extensive therapy."
Was she thinking about him when the recording took place over four afternoons? The look on her face at times during the episode is devastating. "No," she says. "I didn't think of John at all... Only Jim."
That doesn't mean she doesn't care, she says. "It's much easier for me to cry and do all those things on the stage than in real life. Acting is a very strange thing. It isn't about trying to feel, for me, it is about thinking." Was it a question of blocking real life out, to stay in control of every glance and inflection? "Yes. I was taught at my drama school that it's not what you feel, it's what you make the audience feel."
Her school was at the Old Vic just after the war, with the influential French director Michel Saint-Denis. But trying to get her to talk about that – or anything else – in a sustained fashion is difficult as she fusses about with kettle, coffee and those cigarettes. Focus, I plead, and she gives me a stage stare, as terrifying as Lady Macbeth.
"I played that once," she says. I know. Opposite Albert Finney. "My Hedda Gabler was better." The most beautiful creature ever to walk the stage, she was called then. "Who said that?" Nigel Hawthorne, her contemporary. "Oh, he did. Well, I was rather lovely when I was young. That is why I don't like having photographs taken now."
Very few nearly 81-year-olds look as good as she does. But very few can buy clothes with a reported salary of £400,000 a year. Dot is at the centre of the show, having evolved from a nasty gossip into a strong character for whom viewers feel warmth. She is worth her weight in pork scratchings from the Vic.
Nobody thought EastEnders would last when it began in 1985. Dot is one of two surviving characters (the other is loathsome Ian Beale). Every so often she threatens to leave. "It started out as a nostalgic programme about the olden days, but with modern problems. Like the old films, you never went beyond the kissing... and not those awful ones you see now. They eat each other. I don't want to see that!"
Nor does she like the way characters are always "sneaking on each other and interfering". She reportedly told one journalist this episode was her glorious swansong. "No," she says, cackling, "I said it was my Gloria Swanson! You see, you say these things as jokes."
I'm not sure whether to believe her. Dot could go out on a high now. Watching her talk about being evacuated to Wales, the horrors of post-war London and the agonies of seeing people you love die or go wrong will make millions of viewers think of their grans, or their mums, or themselves. It's hard not to feel emotional, watching it. And hard not to think of June Brown's real life.
She was born in Suffolk in 1927, nine years earlier than her character. Her father was wealthy, but he went bust. In London after the war she met and married her first husband, a brilliant actor called John Garley, but he suffered from depression and gassed himself in 1957. Within a year she had married Robert Arnold, who was in Dixon of Dock Green. They were together for 45 years, but since 2003 she has been alone in their big house near Croydon.
The couple had six children. One, Chloe, died a fortnight after her birth. Another, also called Chloe, suffered paralysis, but Brown says it went away after she prayed for healing. She describes Dot as "a kindergarten Christian" but has a strong faith of her own. "If I get a pain in the head I just say a prayer, dear. I put my hands on it and ask for the pure blood of Jesus to flow through it... then I say thank you. You'll think I'm mad."
I think, "you're Dot" as she shows me the little paper cross, prayer card and embroidered orange handkerchief she keeps as props in Dot's black handbag, with a bottle of smelling salts. "Anyone can become a channel of the power, but you have to be pure in heart. I could help people... before this."
She means working on EastEnders. So why has the power left her now? "You get cross and grumpy sometimes, or resentful. You know, you don't get good storylines and you hang around just to say lines like, 'I'll have a tomato juice'. Also, the notes to fans take ages."
Isn't it easier, I ask gently, than a different job in which you might not be so loved, for a much lower wage. But she just looks at me blankly. Then the mood lifts, suddenly, when a familiar voice calls in through the open door: "Hello my darling!"
It's only bloomin' Barbara Windsor standing there, beaming. Not glaring like earlier, when she had her Peggy Mitchell wig on and a look that said "Get outa my pub!" No, this is the smiley Babs that Sid James fell for. "The Independent on Sunday? Posh! And there's me doing quotes for bloody Heat magazine. Ha ha ha!"
Now it gets really surreal, as June/Dot and Barbara/Peggy squabble in high camp style about whether to go for coffee – "don't you reply in that accusatory manner, Bar!" I half expect to see Kenneth Williams. This has been such a peculiar day. "I know I'm old but I've still got a lot of energy, haven't I, Bar? I can put my knees up here," and with that June Brown performs contortions, before leaping up and heading out of the door with her pal. On the way, Babs turns back to say something about the solo show. "Listen, seriously. She is the only actress I know that is worthy of that half an hour. Don't you think she's amazing?"