“Mind you,” she says, eyeing Flott’s tall figure stretched languidly upon the sofa, “you couldn’t do Butterfly on stage, not with your colouring. Do they spend their time burrowing for forgotten material? “Graham’s the burrower,” says Flott. “I don’t think we can take too much credit.” Tonight they are singing with Andrew Davis and the BBC Symphony Orchestra rather than Johnson and a piano This gives them a chance to do more unusual repertoire. The BBC is responsible for most of the programme, which explains the appearance of the Flower Duet from Madam Butterfly by Puccini, a composer neither of them usually sings.

“I’ve been practising Suzuki’s Japanese giggle,” confides Ann mock-seriously. In 1976, accompanist Graham Johnson founded The Songmakers Almanac with Flott, Murray, Anthony Rolfe Johnson and Richard Jackson, performing songs by a wide range of composers, many of which they rescued from oblivion. Everyone except Murray had studied at the Royal Academy of Music, but he had done the final masterclass with the legendary accompanist Gerald Moore in Manchester in 1971, and meeting him again after winning a singing competition, the link was made.Since that time the three of them have cornered this previously disregarded market, singing Purcell, Mendelssohn, Brahms, Rossini, Massenet, Britten and even the odd gleeful piece of Sullivan to remarkable effect. Actually I’ve got such a complex about this one.” “Oh get out of here!” says Murray “No, we have a good relationship. She’s so tolerant of my silly wants and Graham keeps us all together.”It’s all his fault. I don’t sing with anybody else but Flott’s so marvellous, she’s well.. graceful, musical, talented.. you know, sickening.”Does Flott rate her partner? “Naah… It’s nobody’s first choice for a career, least of all theirs.

“Having stumbled upon it though, it’s jolly good fun,” says Murray. “It’s such fun to go on tour and on stage with somebody else You have a freedom you don’t have on your own. You can take that extra risk because you don’t have 100 per cent responsibility The balance moves from one person to the other. Only when singing in unison do they try to colour their voices to blend. On top of the intelligence, sensitivity and musicianship at work, they are obviously having a ball. With its old-fashioned image of stuffy parlours and lace-covered pianos (plus the not-so-lucrative deals), duet-signing is all too redolent of the amateur.

I’ve never been a big fan of seeing Boudicca or Britannia and I don’t have the, er, upper torso for it.” “You could go as her trident,” laughs Flott.There have been celebrated operatic partnerships before, such as Callas and di Stefano or Sutherland and Horne, not to mention the new kids on the block, Alagna and Gheorghiu, but none has done it in quite the same way. Both distinguished soloists with major international careers, they have been touring the world’s leading concert halls from the Met to Madrid and Milan since the late Eighties, giving duet lieder recitals with two highly regarded collections on EMI into the bargain.It’s not just that their voices sound so good together, something they say is unconscious. Murray announces that she isn’t going to try to compete with Walker, who once appeared in a dress that opened out into a vast Union Jack “You couldn’t better that Anyway. Indeed, with just eight days to go, before settling down to some serious rehearsing, they are both distinctly larky, their welcoming grins defying the stereotypical image of the loud, proud diva with massive voice, frame and ego.At Murray’s Surrey home they are wearing jeans but tonight they’ll go for a little more glamour.