There are reasons why Ethos might make you wary. It’s near Oxford Circus, it’s vegetarian, it’s a self-serve buffet and you pay for your food by weight. (That’s the weight of the food, not your weight.) This ‘comida por quilo’ system is a popular economy-restaurant style in Brazil, but it’s been relatively unexplored in the UK.

Adding to the gimmicky potential, on any given day the main menu might include more than a dozen dishes from the diverse cuisines of Japan, Southeast Asia, Italy, Korea, India, Mexico and Lebanon – and anywhere else that does brilliant vegetarian dishes – plus a few of their own creations. You can choose as few or as many as you like, building your own bespoke meal, before having your plate weighed and then paying at the counter.

The concept may seem incoherent at first. Standing by the platters and bowls at the buffet – hot on one side, room temperature on the other – wondering whether the Korean kimchi might go with some nasu dengaku (Japanese miso-roasted aubergine), or the restaurant’s Indian-inflected ‘scotch egg’.

But sitting in the spacious, box-fresh surroundings – the decor is predominantly Nordic white and blue, with some bucolic trunks of silver birch reaching skywards – you taste the food and think: ‘Hang on, this is really good.’

Rather than worrying about whether Thai sweetcorn fritters are complemented by a lovage-laced tomato and bread panzanella salad, the world tour of dishes becomes a mini-adventure in flavour, colour and texture. The own-made kimchi was crunchy, piquant and not too pungent; the tarka dahl was as good as any Indian grandmother’s version. And a warm Lebanese salad of loubieh – fine green beans with tomato sauce – contained just the right amount of warmth from the Arabic seven-spice mix, the cinnamon and cumin clearly discernible. It was with their own more offbeat creations that the kitchen showed a less confident hand – a dish of green lentils and mandolin-thin kohlrabi had good texture, but the flavours were not the best match.

Desserts tend to be crowd pleasers such as US-style cake pops, or small jars of sweet, creamy posset with lemon and raspberry.

Ethos opens early in the day with a short breakfast menu (avocado on toast, fruit salad, granola, porridge), then rolls on through to lunch and dinner, perfect for Christmas shoppers seeking sustenance. Though it’s primarily a lunch spot, the drinks list does include three beers and a dozen wines. Dinner here is worth serious consideration though, because as an affordable vegetarian destination, this is the best one the West End has seen for years.