Hel Yes!, Londonewcastle Depot, 1-3 Wenlock Road, London N1

Had it stuck around, this London pop-up might have been just the place to change our perception of Finnish food

Might it be time for the pop-up to pop off for a while? Where once the idea of a shop or restaurant that's here today, gone next weekend seemed like the dernier cri in spontaneous enterprise, the hijacking of the concept by everyone from Nissan to Liam Gallagher and (hot off the press releases) this year's Masterchef finalists has rendered it staler than a 10-day-old cupcake. Perhaps I'm just bitter because my pop-up dining experiences have left me with the nagging sense of having been defrauded in the name of cool.

Anyway, I seem to be in the minority, because London's latest temp, Hel Yes!, had posted fully-booked notices before it had even opened; indeed, noticeable is the ruthlessness with which my three last-minute invitees axe all other Friday-night plans. Still, Hel Yes! does have a point beyond its own transient exclusivity: set up by the Finnish Institute for the London Design Festival, it showcases the country's cuisine and creativity. And since Finnish cuisine last made headlines when Jacques Chirac named it the only European cuisine worse than Britain's, it's about time we gastronomic philistines clubbed together.

It certainly has the aura of secrecy in its favour: located in a warehouse in a post-apocalyptically quiet corner of Islington, it takes us much aimless wandering to hit on the yellow cement road leading to the entrance. And if what we find inside isn't Oz, it's an evocative space nonetheless, themed upon a camp site and balancing the homespun (candlelit wooden benches, a fruit-and veg-displaying open-plan kitchen) with the forbidding (a Blair Witch-esque video installation of snowy forests, a fibre-optic bat looming overhead). Best of all are the gothicy tables featuring birdcage-like canopies constructed from aspen branches. "Very Tim Burton," I think; "Very Jan Pienkowski," says friend Michelle, the pretentious so-and-so.

And so to the food, described as "primitive", with the emphasis on "pure ingredients". In fact, the kind of Nordic back-to-basics concept that's in vogue thanks to new best-restaurant-in-the-world, Copenhagen's Noma. Yet the thin line between the beautifully simple and the banally simplistic is made evident by our starters. On the one hand, there is the sea-bass tartare, which, despite its minuscule proportions, is as great a raw-fish dish as I've tasted, accompanied by preternaturally tasty croutons of Finnish Archipelago bread, and seasoned with the perfect ratio of salt to lemon. On the other hand, there is the ox tongue, swamped by over-vinegary wild mushrooms.

Thereon in, it's a similarly mixed bag. Two of us have nothing but praise for our bowls of lamb neck, dill adding an inspired tang to the fibrous, stewy meat. However, the other two are indifferent about their choices: a wild-mushroom hash with egg and foraged herbs, in which the eternal joy of a runny poached egg can't compensate for the dull, watery melange of vegetables beneath; and anchovy-and-potato bake, which is perfectly hearty, but less a main than a nice side dish. Finally, for puds, all agree that the raspberry manna – read semolina mousse – is pleasant if unworthy of its divine title, while a liquorice custard proves a true opinion-divider: sludge-like, with the taste of Fisherman's Friend-spiked crème brûlée. Make of that what you will, but I love it.

All the while, the service is what you'd call idiosyncratic. It is 45 minutes before our food orders are taken, while some bread requested to mop up the main course promptly arrives with dessert. A confused cutlery policy leaves Michelle having her knife and fork removed between courses, while the rest of us have to recycle ours. And bizarre, given the primitive ethos, is the affectation of a separate wine waiter; particularly so, when you consider the wine list runs to two whites, two reds, and some fizzes, and that the £25 Vin de Pays d'Oc we order is both unremarkable and tepid.

At one point, our charmingly indiscreet waiter, flustered by our bread complaint, offers, "Sorry about the shambles." Well, it's less a shambles, more erratic, albeit with enough flashes of culinary inspiration to make me hope that London acquires a Finnish restaurant proper. Would I go back to Hel Yes!? Hell... er, probably not: since it closes today, the question of my future custom is hypothetical. Therein, perhaps, lies the biggest problem.

6/10

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

Hel Yes! Londonewcastle Depot, 1-3 Wenlock Road, London N1 About £75 for dinner for two, including wine

Scandinavian stars

Texture

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This Marylebone two-year-old offers an interesting wine selection to match its creative fare – though the décor can seem weirdly bland

Nordic Bakery

14a Golden Square, London W1, tel: 020 3230 1077

Cinnamon buns to die for headline the mouthwatering cakes and excellent open sarnies at this calm and pleasingly different Scandinavian café, just a couple of minutes' walk from Piccadilly Circus

Garbo's

42 Crawford Street, London W1, tel: 020 7262 6582

Hidden from the mayhem of Marylebone, this quiet townhouse – Greta's old home – serves classic Swedish dishes; the lunchtime smorgasbord offers excellent value

Reviews extracted from ‘Harden’s London Restaurants 2011’. www.hardens.com