Chipotle, 114-116 Charing Cross Road, London WC2

One night. Two tables. One hot cuisine. But are the chains opening in the trail of Wahaca taco-tastic or just tacky?

Perhaps Mexican food just isn't one of the world's great cuisines. Or am I missing something in not falling in love with overcooked meat, refried (and refried and refried again) beans, soggy peppers and sour cream, all served up in a greasy giant crisp?

But because I keep hearing that Mexican is where it's at, food-wise, I am prepared to put aside a teenage experience in Oaxaca involving a fried grasshopper and try it. Mexican food – as opposed to Tex Mex, a dirty hybrid that's been fuelling us for decades – seemed to start its renaissance with the launch of Thomasina Miers' Wahaca (yes, that's how Oaxaca is pronounced) in 2007.

The Masterchef champ's mini-chain of Mexican street-food restaurants (if that's not a contradiction in terms) has done much to make us embrace tostadas and tacos, and all over London places are popping up that offer similar fare – with differing rates of success, as we shall see.

Up in the West End on a warm evening, the idea of a spicy treat washed down with a cold beer is very enticing. First stop, Chipotle, the first European outlet of an American "quick-casual" Mexican chain, on London's Charing Cross Road.

It's built for speed, not for comfort – metal-topped tables and chuck-away plates and cutlery. In fact, it's quick- casual in the same way that McDonald's is quick-casual. The countertop display of kept-warm meat and pre-sealed pots of guacamole is a bit dispiriting, but a steady flow of customers suggests it is a popular addition to the area (even if they're overwhelmingly Americans who turn their baseball caps backwards while they hunch over a burrito).

My bowl of barbacoa beef (stringy, but not unpleasant) comes with rice, beans, salsa, sour cream and chillis, which is what all the dishes on offer seem to be – just the meat (there's also pork and chicken, which look unnervingly similar) and delivery method varies. Mr M has the pork version wrapped in a tortilla and it arrives sealed in tinfoil, looking like a bomb. With a beer, lemonade and shared side order of chips and surprisingly zingy, fresh guacamole, our bill is £21.55, which doesn't compare very favourably with Maccie D's, but it was a decent pit stop. I can't hand on heart recommend it as worth a special trip. So, over to El Camino.

This sassy little restaurant has had a Portobello address for a year, but has newly opened a second branch in Soho. I immediately feel on safer ground – the tables are laid with gaudy floral waxed cloths that feel authentic, there's a sun-bleached cow's skull, and one wall is lined with hundreds of different chilli sauces (which seem to range from "ow, ow, ow" to "dear-god-my-jaw-is-melting", although I'm paraphrasing and don't get to find out because the maître d' tells us firmly that they are for display only, thank you very much).

Mr M, who adds chilli to everything up to and including foie gras – and whose dream it is to make Heston Blumenthal's recipe for chilli con carne, if only it didn't take several weeks – feels right at home. He can't wait to get stuck into jalapeño poppers (peppers stuffed with cream cheese and deep fried, £4 for three) and chicharrones (Mexican pork scratchings, £3). The peppers are crisp then creamy, delicious for a mild-mouthed eater like me, but there's no heat. I get a guilty kick out of the cardiac-inducing crackling, but when something's only good when, as the same waiter tells us, "smothered in chilli sauce", I wonder slightly, what's the point? I could be eating polystyrene.

Since we are actually still on the same evening, within the same hour, as the Chipotle meal, I go light with a grilled prawn ensalada (£8.35) but it's a disappointingly generic dish – mixed leaves, tomatoes and olives with five prawns in the middle and a tiddly dollop of guacamole (which doesn't taste as fresh as Chipotle's). Over the table, a pork tostada (£7.95) is similarly modest – two flat discs of crisp tortilla with the usual components. I've always thought the tostada at Whole Foods (an occasional lunch necessity for proximity to office) was expensive at £6.99, but it's four times the size of this.

Well, now I can say I've tried the fad for Mexican, but on this evidence I won't be revising my opinion of it. I'm not suggesting anyone starts serving deep-fried insects, but the next restaurateur to think there's money in Latino cuisine needs to get creative.

5/10 & 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

Chipotle 114-116 Charing Cross Road, London WC2, tel: 020 7836 8491 Lunch and dinner daily. Around £20 for meal for two including drinks

El Camino, 25-27 Brewer Street London W1, tel: 020 7734 7711 Lunch and dinner daily. Around £30 for meal for two including drinks

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