London at night – empty roads and bright lights. Well, it is at that time of the morning. Taxis back home are miles better than the night bus, especially when I'm not the one paying. Keith said he'd put it on expenses and that was alright with me.

He was Chiswick and I was Clapham, which put us both more towards the edge of the transport map than the centre and meant my place wasn't any closer than his at all, but a flatmate wouldn't present the kind of obstacles a wife does, even if I'd had one.

A lot of people balk at the idea of having to cross the river, especially if they think London means North London, but given that we'd met in some pub in SW 14, Keith didn't obviously have that problem. Everything South of the river can be viewed with intense suspicion and sometimes even a curled lip and a 'but it's not really London, is it?'. Mid way down the Northern line is the wilds, or so a lot of City Types would have you swallow.

Clapham's alright. It's got a bit of a buzz going – a long high street with a mix of shops, a few clubs, getting to trendy wine bars and restaurants around the Common, decent shops around the Junction, lots of fried food, taxi firms and takeaways up near Clapham North where I live. Not too many derelict shop fronts, and it's cheaper than closer in, which makes it kind of trendy, with the amount of other young professionals living there.

I'm in one of those red brick deco blocks with square windows and boxy rooms. It's not big. My bedroom's got a slope on the ceiling and the bed's crammed in so you can walk around it just about alright; you can open the wardrobe without any bother. The living room's grand though. It fits my telly perfectly. X box, sofa, beer fridge – sorted.

The kitchen's got about enough room to turn around in and about twenty years ago it was someone's idea of fitted. They crammed a washing machine in, which is brilliant, because even if I only use it when I've run out of everything else clean, I no longer have to go to a laundrette. That is true luxury.

The bathroom's left over from another decade too. It harbours pink tiles and a bad case of mildew. My shower curtain has a half life shorter than it takes to get through a two pint carton of milk. Never mind tar deposits from passive smoking, I reckon my lungs are battling a spore infestation.

It's fine. I mean, normally I'd have said it was a great flat (ignoring the bathroom), especially for the money, but when the guy I'm bringing back owns a five-bed town house in a swanky bit of town, it makes me think a bit different.

So, for the first time in fucking ever, that's what I find myself worrying about while we're in the taxi cruising over Vauxhall Bridge. Twinkly lights, Thames all dark and rippling, Keith's got his hand on my cock rubbing me up exactly the right way through my work trousers, and in between wondering whether he'd have a problem with me sucking him off in front of the taxi driver, I'm forming plans to keep him out of my bathroom so he never has to face the black mould eating up my shower curtain.

"Piss out of the window. Really. Go for it mate. It's tradition round here. Hate my neighbours anyway."

With a pair of raging hard-ons we got out of the cab like nothing at all was going on. Habit, I guess, but it must have looked a little strange to the taxi driver after the show we'd given him in the rear view mirror – the pair of us standing a respectable distance apart, walking together but not touching at all – hands in pockets - even though it was obvious we were going inside to shag each other senseless.

"Nice place," Keith muttered once we'd got up the stairs and I'd let us in, glancing back to see me close the flat door and set my keys down. I shrugged and blanked that – who did he think he was kidding?

"You want a drink?"

He rocked back on the heels of his shiny black shoes and matched my shrug. "Sure. What have you got?"

In the kitchen, I dug a couple of beers out of the fridge, cracking them open before handing Keith one of the bottles. His smile went a touch more intense and I realised he was standing a bit bloody close, even for the size of the kitchen. No complaint, mind you.

"So..." Leaning against the counter, I took a swig from my bottle and let my eyes trail down his chest, coming to pause at the buckle of his belt.

He huffed a snorted laugh, soft, but definitely at me. "So..." he echoed, flashing his eyebrows higher. "Need some ice on that?"

One mouthful of beer and he stepped even closer, eyes flashing wicked as he pressed the wet, cold bottle against my dimly pulsing cock and I gasped.

"Fuck." Some involuntary reaction made me start back, but with the counter hard against me, there was nowhere to go. "Fuck off!"

I squirmed, pushing him, tugging at his arm – almost laughing, but more from disbelief than because it was funny - and he held me there, free hand wrapped tight around one of my wrists, the whole of his body weight pinning me. And then his mouth stopped all the noises I was making and he let the bottle shift. My hand left mine on the counter top and he must have nudged his next to it because next thing I knew I had one hand firm in his hair and the other arm along the length of his shoulders, slightly up on the counter with my thighs clenching around his sides, absolutely throbbing.

We made it out to the living room again and started on another triple pack of Johnnies right there on my Ikea rug. We shagged our way through to daylight, ending up on my bed eventually. Not a lot of orgasms, just a nice long time getting to each one after the first quick fuck. There was some dozing in between, but mainly it was kissing, fondling – talking a bit, but not about much.

Come half five in the morning we were both pretty shagged out and he was having a smoke out of my window, while I lay sprawled against my pillows, arms behind my head. He'd grabbed a pack of Dunhill Internationals out of his jacket pocket and was standing there starkers, catching his ash in the old water glass he'd picked up that I'd left on the bedside table the night before.

"How's your kid?" God knows what made me ask that; I'm never normally one for meddling.

He looked back, frowning while he tapped his cigarette gently enough to need rolling against the edge of the glass for the ash to fall away. "Kid?"

"Peter," I clarified, that awkwardness about poking my nose in filtering through, despite the lack of sleep and beer jacket. The confusion was focused on my question – I reckon more the fact that I was asking than that he'd suddenly forgotten he was a dad.

"Oh. He's... fine. Why?"

My shrug stretched slow; saying I didn't give a shit, I was just playing the small-talk game, but my social filter had malfunctioned into making it seem alright to ask about my latest shag's kid, didn't feel like it would wash, even though it was the truth. The silence had stretched a little long and I'd done a mental flick through of all the things I knew about him. Suits on a weekend, worked for a company posh enough to spring for drinks, lived in Chiswick, had a kid. " Uhm. He knows, you know?"

Keith's eyebrows shot high and he stared at me hard, then he scoffed, looked down at his cigarette, out of the window, back to me. "No he doesn't."

Denial: it's a strange beast. Keith's lips were in a very solid you're-an-idiot-Martin smile (the kind my boss gives me sometimes when he thinks he'd right) and he shook his head again, giving that little laugh.

"Yeah. He does." I kept my eye contact firm enough that he had to realise I was being serious and the smile wiped off his face so quickly even I felt queasy. Cigarette forgotten, he tugged at his hair and I've never seen a man look more trapped.

Fist clenched and finger pointing, ash-glass and smoke both grabbed in one hand, even a naked man can look pretty threatening when he's on the edge. "Look, Martin. I don't know what you think your game is-"

"Oh fuck off!I didn't bloody tell him."

The tight fist unclenched, going up to press against his eyes and then smudging down his face on a loud exhale. "This is none of your business."

"Mate, I'm not trying to make it my business. First thing he said to me – 'you the guy dad's shagging?'. Honest to God."

Keith slumped down on the edge of the bed, feet flat to the floor, wind right out of him and I felt just a tad guilty. He shook his head, looking at me with eyes that were getting a bit too close to glassy for my comfort levels. "I love my wife. I do. He knows that. It works for us."

"Sure you do, mate." I breathed out, shaking my head slightly but keeping back the laugh as I reached for his shoulder, squeezing the tension from the slope, trying to be reassuring. He thought he was telling the truth – anyone could have seen that. "And that's great. Really. No offence, yeah? But I'm only after your cock. Just giving you a heads up, ok?"

Keith gave another sigh, leaning forwards to rest his elbows on his knees, head in hands and for a minute there I thought I'd gone and walked myself into a full-on dig him out of a guilty conscience session, which was really not how I'd planned on spending my Saturday. But then he snagged his boxers and sat up.

"It's what? Nearly six. I'll catch a first train if I leave now."

I shifted on the mattress, leaning back against my pillow again, feeling a surprising amount of relief he wasn't planning on hanging around. The best one night stands are the ones who know when to clear off.

"Yeah. Yeah, makes sense. Nearest tube's Clapham North. Right out of here and then along the high street a bit." He didn't ask for breakfast or a coffee and I didn't offer him one; it would only have made him miss the train he was going for.

"Great." I reckon he probably didn't have the first clue about how to get back from Chiswick from there, but I wasn't going to baby him through directions. If he was desperate enough he could get a cab. If not, it was exactly the same slog home I'd made after that first time, only reversed: Northern Line to Balham, then the overground with a change and Clapham Junction, dicking about on an empty platform for ages waiting for the connection to come in. No way would he be back home before seven.

Watching him put his suit back on and try to neaten himself up turned me on a little more than I like to say.

"Hey, Keith?" I called, making him pause on his way through my bedroom door. "Give me a ring whenever you're up for a repeat."