Last night was my Mother’s Day Eve celebration with my son: he had tickets for us to see La Boheme at the Royal Opera House and suggested we eat first in one of our favourite places, Wahaca, in nearby Chandos Place. Neither of us had been there for a while. Part of the problem has always been the queues. When Thomasina Miers opened this, her first Wahaca, in 2007, serving Mexican street food, it was one of the first serious eating places to have a no-booking policy. That’s become quite a trend and although there is a fun aspect to it and one avoids ridiculous attempts to book a table ages in advance, it does have drawbacks. But then again, this is ‘street food’, not haute cuisine, so the no-booking policy makes sense.

Even at 5.40 last night there was a long queue and a half-hour wait. However, we were prepared; we had time! Just. The queueing system once there is very efficient. Your name is taken and you are given a hand-held buzzer that will let you know when your table is free while you go to the bar and get a drink. It was busy and buzzing and the atmosphere is great. Though we joined the deep queue to the bar, a waiter came and asked us what we wanted, took money and went and got the drinks for us – and very quickly. Soon we were sipping at the ‘must-have’ drink when I go to Wahaca – Tequila Mojito.

I rarely drink cocktails or anything stronger than wine, but mojitos seem the only way to go at Wahaca and these are wonderful. Our table was soon ready and we took our drinks to the table. We weren’t intending to drink more alcohol – neither of us wanted to be sleepy in the opera – but these long drinks would last the meal.

Once at the table we were reminded of another Wahaca policy: food comes as it’s ready and even though you may order ‘starters’ and ‘main courses’, they don’t necessarily arrive in the usual order. That’s not normally a problem, because before that’s been pretty much how they’ve come. But after the waiter had taken our order I heard the next-door table say that since they’d finished their main course and their starters had never come, they wouldn’t bother to have them. They then ordered dessert but the waiter soon returned to say what they’d ordered was off the menu that night … why hadn’t he known?

First to arrive at our table was Huitlscoche Quesadillas – toasted tortillas filled with sauteed mushrooms, Mexican corn and melted cheese.

The filling was delicious: creamy and garlicky. However, they were almost cold: lukewarm filling in cold tortillas on a cold plate. Our other ‘starter’ arrived; a daily special: Camitas tacos – ‘succulent confit of pork cooked until it’s meltingly tender, then caramelised on the grill. Served on soft corn tacos with tomatillo salsa, coriander, onions and a wedge of lime’.

The taste was spectacular: everything that is good about food at Wahaca … except that like the quesadillas, they were almost cold. Again, the filling barely lukewarm and the tacos and plates cold. I don’t think the plates being cold for ‘street food’ is a problem if the food is sizzling hot. Isn’t part of the point of street food being that it comes straight from the grill or whatever it’s being cooked in or on straight into your mouth? Shouldn’t it be hot? At almost the same time Jonathan’s ‘main’ arrived. I know they don’t term it a ‘main’ but most people do. I guess if you’re in less of a hurry than we were – not a great hurry but we did have to get to the opera on time – you could order small plates to share for starters and then a big plate main later, but even so, it seemed to us there was no reason at all for Wahaca not to at least ask if you’d prefer your small plates first? It can’t be such a big deal to give the customer what they want.

Jonathan’s British Steak the Mexican Way looked wonderful and he said it was good … except … yes, here I go again, I’m afraid … it wasn’t cooked rare as he’d asked for but was medium; the steak was hot but again the plate cold. Strips of steak are going to go cold quickly on a cold, cold plate. My main didn’t arrive until his was nearly finished. I was definitely feeling irritated now. We were also feeling irritated because we’d asked for tap water when we sat down and it hadn’t come. We asked again and still no luck. We asked a third time and only managed to get some when our bill was brought and we asked a fourth time!

My main was a Wahaca ‘Classic’ – MSC Fish Tacos: ‘crispy fried MSC (certified sustainable) plaice goujons on a bed of new crunchy salad mix in a soft tacos with chipotle mayonnaise, guajilo oil, crema mayo mix with beans and rice’. I’ve had this – or similar – before and it’s delicious but in tune with the rest of the meal, only lukewarm. The goujons were hot – not sizzling – and of course of salad should be cold, but the tacos were cold cold and even the rice and beans lukewarm with a film across the top that made it look as if they’d been sitting around for a while rather than freshly spooned into the small bowl when serving. The side salad in a small bowl was OK but I’ve had more interesting ones there before.

It was such a shame. The food tasted good: Thomasina Miers (who I’ve always liked and admired) has got the flavours spot-on but the service was appalling. Jonathan said he was now reminded why he hadn’t been there for a while. It was my worst experience at Wahaca and it seems to me they’ve lost the plot: they’re busy churning out food – delicious as it is – to the crowds and the kitchen and waiting staff are letting things down. I don’t want to have to ask four times for water. I don’t want to eat food that should be sizzling fresh lukewarm. At it’s best, Wahaca is brilliant and I know I’ll be back to try it again because I love the taste of the food. But if I keep getting such a bad service experience then I will stop going because I don’t want to be irritated by things that are so easily put right. The service was just sloppy. My son quietly complained to the waiter and he blamed it on the kitchen. Well the kitchen needs to get their act together better, but the waiter also needs to bring water to the table when asked and not have to be asked four times.

Fortunately the opera was definitely on form and absolutely brilliant!!