Tariq calls at eight the following morning, bringing me back from a deep sleep. Twenty minutes later I’m on Royal College Street, ducking into the Renault 5 I bought for almost nothing from a man who had been upgrading to a family estate, the week I passed my test. He’d looked mournfully at my open palm as he handed over the keys and I’d wondered whether it was the old banger he was sad to say goodbye to or whether he was thinking of the passing of his life as he’d known it.

Even at this early hour, the sky outside is a piercing blue, glowing with some sort of promise. Swinging my bag onto the front seat next to a pile of old magazines, empty cigarette packets and discarded cans, I turn on the engine and watch a jet-stream of dust shoot out from the fan.

Tariq’s information had been sparse – more of a vague location than an address – yet as I make my way through Kentish Town, along Fortess Road and down Tufnell Park Road, there’s a feeling of anticipation.

At Holloway Road, I turn right and then left onto Seven Sisters, past a patchwork of churches and mosques. Going left at Finsbury Park past endless roadworks, I finally pull up outside a cluster of shops lining a quiet curved road. There is the greengrocer’s Tariq had described and, next to it, the social club, which he suggested, without using as many words, might be a cover for something more dubious.

With nothing else to do but sit and watch, I pull into the mews opposite, turning off the engine and setting my eyes on the social club, reminding myself, when the doubt threatens to cloud my conviction, that I have broken cases with more tenuous leads than this in the past.

The building in question – indicated by a handwritten sign in childish writing above the door – is an inconspicuous if unconvincing affair, the wide windows in the front concealed by frosted plastic sheets.

I sit and wait, the rush of adrenaline subsiding as the minutes pass, until two hours later I am desperate for caffeine.

Pushing the car door, which resists and then opens too fast, I pat my pocket to check for change before crossing towards the greengrocer’s. The bell above the door tinkles as I step inside, and my eyes struggle for a moment to adjust to the relative darkness after the blazing sun in the street outside.

Moving straight for the fridge, I pick up a Red Bull from the shelf before heading to the counter to pay. The woman at the cash desk is deep in conversation with another customer and I stand there for as long as I can bear before clearing my throat.

‘Just this,’ I say, placing the right change on the counter, cracking open the can as I move back out of the shop.