Meateasy, above the Goldsmiths Tavern, 316 New Cross Road, London SE14

Tim told me to go to Meateasy – everyone's talking about it, he said – but since he's much younger than me, I felt no compulsion to follow his advice. I am allergic to hype, which is why I haven't yet seen The King's Speech, bought Adele's new album or taken a holiday in Berlin.

Then there's the location of this pop-up wonder. It's New Cross – a part of London I can't really identify, never mind find. Is it east or south? Isn't it one of those places without a Tube station? I think I'll leave this one to the hipsters (sorry Tim). But then – and I'll be honest – a deadline looms that coincides with a lull in the frenzy of new London restaurant openings. So on a dismal night, I'm off across town to SE14.

Some background: Meateasy is the non-moving offshoot of Meatwagon, a wildly hip travelling burger bar, but with brilliant-quality produce and fun attitude. Yianni Papoutis runs the Meatwagon, but alas the van has been pinched – so a deal was struck with a closed-down pub in New Cross to use the upstairs as an unofficial restaurant till the developers moved in.

Twitter – another much-heralded thing that I stubbornly ignored for ages, but am now embracing – reveals with how much esteem Meateasy is held. "The only thing getting me through work today is the thought of #meateasy," tweets a fan. "My life isn't complete till I get to #meateasy," says another. Visitors are evangelical.

Naturally we baulk at the sight of a dingy, dark pub on the verge of two lanes of pelting cross-London traffic. There are NO signs of life. Look closer, and a chalkboard propped up on the pavement says, "Congratulations, you've found Meateasy." We enter a side door, through a scummy corridor and up some bare stairs, with only graffitied signs to show us. It feels like this could be a Saw movie, with the meat in the meateasy being us.

But swing open the heavy door and a hot, heaving, buzzy room reveals itself. The joint, as they say, is jumping. The walls are papered with paperback pages – I spot Fear and Loathing (of course). It's dimly lit, and mismatched tables, chair and sofas are spread higgledy-piggledy. There's a bar in one corner, and the only bright spot is a kitchen ablaze with light and activity. "Take a ticket," says our hostess. "When we call your number, you can come and order."

It all adds to the slightly underground feel – and when we're drinking out of jam jars and craning our necks to see the dishes scrawled on the wall, it definitely has the speakeasy vibe.

Of course, it's all about the meat. Philly cheesesteaks, burgers: cheese ones, bacon cheese ones – plus the eye-popping "dead hippie". This delight is two mustard-fried patties with lots of cheese and special sauce – I never do discover what they put in it, but I want another straight away. I hope it's not an addictive substance the hippie had in his pocket when he died...

We also try chilli cheese fries, mac and cheese, buffalo wings and onion rings. Almost everything has a mustardy tang that makes it moreish. The chicken is sticky and spicy, and they're generously fleshy wings. The mac and cheese is crusty on top, with a molten swamp of mature cheddar and Parmesan-enriched sauce. For £5, it's a meal in itself. The dead hippie (£7.50) is also a total bargain – the meat is coarse-ground and well-flavoured, with juices that muddle with the sauce and run down your wrists. Luckily there's a kitchen roll on every table. Almost everything is disposable – the cutlery, plates and tubs holding 'slaw.

The thrum of the crowd never lets up. Every table is taken and as soon as it's vacated, another group emerges from the darkness to take it. "This is as quiet as I've seen it," says the hostess, chirpily. Almost everyone is drinking lageritas – margaritas with a Meantime wheat beer top – which definitely has the effect of turning up the volume as the night progresses. At one point a waitress puts on a Mexican wrestler's mask. I think.

When we wearily stagger out, full to the brim with the very best of fast food, there are eager punters waiting to pounce on our table. If the landlords really do boot out the Meateasy crew in April, some other property owner should use their initiative. Mind you, with trade that brisk, a shiny new meatwagon could be on the cards. And, in the Twitter parlance, a hat-tip to Tim Walker.

twitter.com/lisamarkwell

7.5/10

Scores: 1-3 stay home and cook, 4 needs help, 5 does the job, 6 flashes of promise, 7 good, 8 special, can't wait to go back, 9-10 as good as it gets

Meateasy, Above the Goldsmiths Tavern, 316 New Cross Road, London SE14, themeatwagon.co.uk Open to 16 April, 6pm-11pm, Tues-Sat; cash only, no bookings. £40 for two, including drinks

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Reviews extracted from 'Harden's London and UK Restaurant Guides 2011' www.hardens.com