I scanned my list of names again and found her address. The number matched the rust-bitten silver digits screwed into the black door and I consulted my paper to find her flat letter. I leaned on the “A” doorbell and stepped back, waiting for the little box beside me to squawk into life with my patient’s voice asking who it was.

I locked eyes with a landscaper working in the neighbouring garden and flashed him a smile. He nodded, a recognition of a fellow community worker navigating the maze of London houses and apartments.

When the response finally came, it wasn’t from the direction I’d anticipated. The metal box remained silent and instead a wavering voice drifted down from above.

‘Hello. I’m up here.’

I glanced up to find a thin elderly woman in her nineties leaning out from an upstairs window, a bird-like hand waving at me, and a toothy smile grinning down at me. It was instinct: I waved back.

‘Hello,’ I said, remembering why I was there. ‘I’m Jonathan, the community phlebotomist. I’m just here for a blood test. You must be Catherine.’

‘Oh, right you are. I’m not good on my feet. I’ll have to throw the keys down.’

‘Oh.’ This was new. ‘Okay, sure,’ I said to an empty window, my patient already disappearing inside.

I rocked on my heels, waiting on a stranger to throw her door keys at me, and shared another look with the landscaper. I gave a weak smile and glanced away, repressing the urge to tell him this isn’t how it normally went.

After five minutes the frail face reappeared in the square of window frame. ‘Oh good, you’re still there. I’m throwing them down now.’

I raised my arms above my head and clapped my hands. ‘Go ahead,  I’m a good catch,’ I said, then felt an absurd surge of anxiety that I’d drop them with the landscaper watching. I couldn’t tell you why I wanted to impress a stranger with my key-catching abilities, but there it was.

Catherine gave a little flick of her claw of a hand and the keys hung in the air. I traced the arc of the descent with my eyes and my hand snaked out, snatching them from the sky with a contraction of my fist. I felt a flood of elation and sneaked a glance at the landscaper to see if he’d seen. He gave a raise of his brows and I shrugged like it was no big thing.

‘It’s just the one by the handle, and then the bigger one unlocks the lower lock.’

Catherine’s words snapped me from my victorious reverie and it occurred to me to put the keys I was still holding aloft like a trophy to use. I followed my patient’s instructions, unlocking deadbolts and locks with keys straight out of the Victoria era, big fat keys with the small square of teeth at the end. I stepped inside and into an apartment that could have been lifted from a Sherlock Homes’ novel. Sunlight filtered through the dusty air and a rug-lined staircase twisted up through the wooden foyer to the bedroom above.

I mounted the stairs and found my patient sitting in her nightie and dressing gown on a two-seater couch that looked as old as she was. She looked small in the big bedroom instead of the image I previously had of her hanging out a window.

‘Catherine, it’s nice to meet you,’ I said, handing the keys back, stupidly triumphant in this exchange of property, as if it was a challenge I had risen to and won.

I slipped into my role of health carer, providing the necessary small talk and questions while simultaneously preparing equipment and poking this sweet old lady with something sharp. If done well, you can have your patient more absorbed in the conversation than the act of taking blood, and they’ll swear afterwards that they didn’t feel a thing, even if in the moment they winced as the needle pierced flesh. This I treat as a real triumph — the ultimate victory.

I completed the necessary paperwork and Catherine fell silent as I worked. When finished, I looked up to find that she had a portable phone in her hand.

‘The council are always so hard to reach,’ she said.

‘Tell me about it,’ I replied while slipping on my backpack. While I’d never tried to reach my local council in London, I felt I’d waited on-hold long enough with equivalent organisational bodies to share an eye-roll at the ineptitude of Catherine’s local council.

‘I just ring the gas-leak number,’ she said with a wicked and satisfied little smirk I wouldn’t have believe this old dear to be capable of, and she pressed dial on her phone.

I laughed and gave her a silent tip of the hat, and as I waved her goodbye and turned to head down the stairs I heard this exchange:

‘Hello! No, no, there’s no gas leak. I just need more of those green compost bags…Oh, you could? Oh, well, thank you, dear.’

As I made my way down the stairs I couldn’t help shake the feeling that there was a lot Catherine could have taught me about navigating life in London.