Nearly 40 people are gathered here, some perched on little plastic chairs, the rest squashed into ancient sofas. A child sits silently in the corner with a chaperon, doing puzzles. And a man is trying - and failing - to control his grief over the death of a boy in battle.
It is the read-through of the 10th and final episode of Radio 4's forthcoming dramatisation of War and Peace. Emily Mortimer, small and frail-looking in black, has been reading Natasha's part in a low, rapid monotone; the voice of Daniel Evans, the 15-year-old playing the impetuous young Petya Rostov, has been developing urgent courage as he hurtles towards his death; in this episode, at least, Christopher Scott's Denisov has stolen the show. He has heroically - and somewhat comically - mastered the speech- impediment written into his script, saying things like "We might as well pwoceed to the fowest hut". Now, he is sobbing helplessly: "I told you to keep back, Petya ... I told you to keep back." The assembled company is completely silent.
In Tolstoy's novel, Denisov is a colonel in the Hussars. And this Classic Serial is being recorded next to a famous restaurant called The Gay Hussar. For a decision has been made to record this drama not in a soundproof studio, but in a house in Soho, central London. Among the notorious pubs, the grim old sex shops and the private-view cinemas, the House of St Barnabas at No 1 Greek Street alone retains its original architecture. Perhaps because it has been a charitable establishment since 1846, nobody has got round to developing it.
It is a splendid place, all flagged stone floors, wildly exuberant plasterwork and extravagant staircases. In the Council Chamber upstairs, four fat and beaming putti frolic on the ceiling, while a faded Turkey carpet makes a brave attempt to cover acres of floor. The Records Room along the corridor houses shelves full of tatty leather-bound volumes. You can pull them out at random and read beautifully hand-written, meticulously detailed accounts of the daily visits of doctors to the poor of London in the 1840s.
The house is still a charity which shelters deserving ladies down on their luck, just as in Gladstone's day. To help pay its way, it lets out these stately rooms to anyone who wants them: in this case an outside- broadcast unit of the BBC. So absurd is the system of accounting at the BBC that the hire of one drama studio would have cost 10 times as much as this house. But although recordings were bedevilled by the racket of traffic and road-drills, the house exuded an atmosphere that almost made up for the aggravation. The high ceilings and echoing floors, the sheer beauty of its architecture, gave the cast and directors alike a sense of drama entirely appropriate to the project.
Simon Russell Beale is playing Pierre Bezuhov, to his great delight. "He is just such an enchanting character - so good, and so troubled. Good men in novels are rare." Abigail McKern is Maria Bolkonska, whose very serious attitude to religion makes less immediate appeal to our cynical age. But "She's no wimp," insists Abigail. "You see that when she stands up to the peasants. People with strong faith can be very interesting. And her happy ending is just right. I'm beginning to feel that home and family are the most important things. Besides, poor Maria has a monster of a father ..."
Abigail's own father, Leo McKern, is the narrator, in the person of the Russian General Kutuzov. The two writers who adapted the book, Marcy Kahan and Mike Walker, chose that technique, agreeing, says Kahan, that "you have to change the form of the novel to turn it into a drama, but you must stay true to the inner spirit of the book. You must never patronise it or laugh at it." Kahan is utterly delighted with the whole thing. She had already adapted Little Women, Anne of Green Gables, The Wizard of Oz and The Railway Children for radio and she was tiring of the nursery. "I wanted to sit at the grown-ups' table," she says.
The two writers have had great fun with it. The best running joke evolved from an earlier dramatisation, made some years ago, when two extras ad- libbed during a ballroom scene and one famously remarked: "They say that Pierre Bezuhov has the biggest balls in Moscow." That's a line the writers have added to every episode, chortling as, each time it appears, the actors deftly sidestep it.
The extras in this version are members of the stalwart and adaptable Radio Drama Company. Ioan Meredith, for example, has played at least a dozen parts in the production. He is the man who introduces Pierre to the Freemasons, an old Bolkonsky servant, a Russian prisoner and many more. He doesn't mind how many roles he is given, unless it reaches the point where two of his characters share a scene and he ends up talking to himself. That he says, can get a bit awkward.
Alison Pettitt is, at 22, one of the youngest members of the RDC, "radio's rep". She is playing just one part - in this production, Natasha's sister Sonya. Dark and slight, she sits cross-legged on the floor and enthuses. She loves radio acting. "You have to focus on your voice entirely," she says. "It's a really good discipline - and besides, you get to play things you'd never do if people could see you. In other plays, I've been a freckly blonde eight-year-old, a 40-year-old Londoner and a large, busty Lancastrian lass." Simon Russell Beale agrees. "It's only on radio that I'll ever be given the chance to burst through a door and say, Unhand that woman!"
The direction is shared between Janet Whittaker and Eoin O'Callaghan. Today, Whittaker is doing the donkey-work. We troop upstairs to the Council Chamber to polish up a moment from episode nine. She asks some of the company to make background conversation - "but subdued please, concerned - not cocktail chatter. Try not to laugh. Remember, we've just had the Battle of Borodino." They oblige with perfect professionalism.
In the foreground, under the smiling cherubs and the huge chandeliers, Hugh Dickson and Janet Maw (swishing about in a long pink silk skirt) perfect a tiny scene which serves to move the plot along by recounting the death of Pierre's first wife, Helene, from drink. Maw is playing Pavlovna Scherer. Delicately, "It was ... angina?" she enquires, her voice conveying the right degree of polite concern, laced with innuendo. As Helene's frightful father, Dickson stutters and prevaricates, torn between sorrow and shame.
As he speaks, I work on remembering where I last heard that voice. Ah yes, this is the man who played the late-lamented Guy Pemberton in The Archers. How nice to have him thus resurrected. But the traffic has built up and the scene must be played again. We wait for a car, then a motorbike, until at last it is quiet enough to risk it.
In the corridor outside, another member of the cast, Anthony Ofoegbu, is busy strapping on some spurs: there's another battlefield confrontation on its way. They were right to come to this place. As he stamps and jingles off down the broad sweep of the echoing stone staircase, he sounds exactly like a Hussar.
'War and Peace' (R4) starts today. It is also available on cassettes from BBC Worldwide (pounds 30).