Delia is slicing tape into tiny pieces at near midnight when the lady calls upon her.
"Miss Derbyshire?" She blinks up from her razor-blade jig, eyes sore from too much fluorescent light, and sees a middle-aged woman carefully turned out in tweed smiling faintly at her.
Delia frowns. There is something familiar... ah! Years ago, in Geneva, drunk on peach schnapps at an embassy party and pouring her heart out to one of the diplomats' secretaries... "Peggy Carter?"
"It's Hill, now," says Peggy. "I remarried some years back. How have you been?"
Delia gestures around the clunky apparatus of the BBC Radiophonic Workshop, "Not teaching piano and basic mathematics, as you can see." She smiles. "It took a while, but I shoved my way through one of the closed doors in the end. But are you just here for a cup of tea and a catch up?"
Peggy hands her a reel of quarter inch tape. "I need you to tell me if this is real."
Delia shrugs and threads it through a player. There is a short staticky clip of train sounds, and the echoing noise of a busy station. Two men speak with the fond familiarity of long friendship: -at's what Dr Erskine always said, don't try to be a perfect soldier, be a good man... I hear ya, pal...
She plays it again, and a third time to be sure. "No," she says.
"Are you sure?" Peggy says, eyes intent.
Delia rises and searches through her sound-effect library until she plucks down the tape she needs to demonstrate and runs it. "It's the standard Euston Station clip of ambient noise; I'd know that pattern of train whistles anywhere. You can hear how they cut out just before the announcement starts in the original clip. And the static is a touch worse when the first man is speaking - it's a sound clip that has been copied too many times and the quality is lost."
She adds, "You wanted a 'yes', I think."
"Harsh truths are generally preferable to cheery lies, I've found," says Peggy. "And a firm negative can be useful." But her eyes hold hurt and disappointment, and she looks suddenly tired.
"I'm sorry," says Delia. "Time for tea."
Later, when both their hands are wrapped around earthenware mugs of steaming black tea cut with honey, Delia looks at Peggy's hands, covered with scabs and the raw pink of healing burns and remarks, "You were never a secretary, were you?"
"I type a respectable 65 words a minute, thank you."
"Am I ever going to find out what this was about?"
"Oh, I doubt it. What are all these machines for?"
Delia gestures around the oscillators, variable-speed tape decks, and re-recorders. "Well, right now, I am going to take the recording of one plucked string and a few tuning forks, speed them up, slow them down, slice them and piece them, and turn them into a tune for a new sci-fi show. It's finicky, awkward work and (when nobody is watching) I swear at it. Quite a lot, actually. Who knows if the show will even take off - I've given up predicting which ones catch an audience. But when I am done I will have made something..."
"Rich and strange?"
They flash identical toothy grins at each other.
"Are you happy, here?"
"Oh, yes! I'm mixing music and mathematics and making things never heard before. I love it."
"Well," says Peggy, handing her a card, "if you ever become not-happy, give me a call. My employers always have room for a pair of sharp ears and a brain to use them."
"If you like," says Delia. "And - good hunting?"
Delia found herself calling the number on the card a year later, though - not about that job...