We arrange to meet at the gates to the university, on Gower Street. At the flat, I pull on jeans and a pale blue shirt. Through the window, there is a blue sky and a light wind brushes the tops of the trees.

It is just past 9.30 a.m. by the time I leave, my hair still damp. Deciding to make my way on foot rather than take the bus, I walk past Mornington Crescent, turning left past Euston, avoiding the more direct route along the endless grey and brown façade of Hampstead Road.

We arrive within a minute of each other, his linen suit weaving precariously across the busy road towards me. He has that unmistakable whiff of academia, old books and stale coffee.

‘Shall we go to my office?’ he says. Once inside, he directs me towards a studded green-leather chair. Sweeping across to the other side of the desk, he assumes his position with his fingers crossed over each other, his elbows jutting out to the sides.

Following his cue, I reach my hand into my bag and pull out my phone, as well as my laptop and a USB stick. A few minutes later I turn the sound on my computer to full volume. As the fuzzy sound of the recording fills his office, ricocheting off a wall-to-ceiling bookshelf stuffed with thick leather spines, there is the distinct sound of men talking in the background of the recording.

A few seconds later the man’s voice kicks in and at this volume his low growl makes my flesh crawl. From the timbre, it is almost certain that he has used some sort of voice-distortion technology.

Professor Mansfield’s eyes move in my direction as the recording stops. ‘Interesting,’ he says after a moment of silence. ‘Where did you get this?’

‘It’s a long story, it’s to do with a piece I’m working on,’ I lie. ‘The thing is, I really need to know what language they’re speaking.’

There is no point embroiling him in the truth of it. In my experience, too much truth has a way of making people feel uncomfortable; the trick is to give them just enough.

‘May I listen again?’

The enthusiasm in his voice makes me sit straighter, and I nod, smiling, as I drag the cursor back to the beginning of the recording.

Again, there is a low hissing sound and then the men’s voices, which seem clearer with every listen.

‘Well, I have an idea,’ he says eventually, rubbing his chin with his fingers. ‘But if you don’t mind, I’d like to seek a second opinion.’

‘That’s wonderful,’ I say. ‘I can download a recording directly to your computer.’

‘Very good. I’ll have a word with a colleague and I’ll be in touch,’ he replies briskly, once it is done, before showing me the door.