Sublime modern Indian cooking in the most glamorous ‘basement in Sloane Square.

Blink and you’ll miss the entrance to Kahani, it’s part of a smart mansion block down a small side street, and about the last place you’d expect to find a restaurant.

The tight entrance leads to a staircase as steep as the conning tower ladder on Das Boot; hang on tight or one misstep will have you sprawled at the bottom in full view of Sloane Square’s elite. You don’t want that.

The room that appears is a pleasant shock, it’s very large and it must run underneath the whole mansion block that’s above, it’s airy and light though and there’s no sense of being underground.

And it’s buzzy; even as early as 7pm it’s all but full. We’re lucky to get a table under what appears to be an ancient stone fireplace presumably pillaged from a French Chateau. That would make sense as this was once a French Fine Dining place.

Can I review chairs? I’m going to, my chair is so soft, so embracing I just sit and enjoy it for a few minutes, even luxuriously stretching my legs out and becoming a hazard to the busy but friendly waiters.

The menu is a biggy, divided into so many sections –  a la carte, tasting (vegan and non-vegan), pre-theatre, lunch, bottomless brunch, tasting Dawat etc – that my head spins.

Chef ​​Peter Joseph, was once head chef of Tamarind, the first Indian restaurant in the world to win a Michelin star and it shows.

Order what you know is, like ‘write what you know’, very bad advice; where’s the chance of finding something new? That said, I know that I always like Papdi Chaat, a classic street food that I’m keen to try in a high end restaurant.

|A beguiling blend of spiced chickpeas with sweetened yoghurt, mint, tamarind chutney, papdi (wheat crisps, although I have also had it with Rice Krispies which works surprisingly well) it is refreshingly cool and the tamarind and yoghurt combination a real palate livener. Not so much street food as Sloane Street Food.

We chased this down with soft shell crunchy crab with Mangalorean spices, kachumber salad, enlivened by dabs of smoked tomato chutney. The salad was more like seasoning/decoration than food, adding colour to what is otherwise a fairly non-instagrammable dish.

The crab doesn’t need any more followers though, it’s already a star. Mangalore is a coastal town and they know how to use seafood there. Here the local spice blend picks up the essential sweetness of the crab and plays along with the smokey sauce.

Seafood also washes onto the table in the curled commas of two smoked Malabar prawns marinated with fresh turmeric, coconut and curry leaves. Big and ‘meaty’, kissed enthusiastically by flame and very good to eat with our fingers popping the last bit of meat out of the shell ‘handle’..

Not everyone likes broccoli, children and ex-President Bush can’t stand it, I think that’s because they have only ever had it boiled to a pulp. Broccoli relishes being roasted and charred especially in a tandoor, as it is here, after being marinated and dressed with honey, nigella seeds and wheat crisps.

So far so excellent but here come the lamb chops. I believe it was Chef Atul Kochhar who first elevated these to culinary heaven back in Benares days, although he also of course once also worked at Tamarind. The price was elevated too, I think it was £21 for two and that was about thirteen years ago.

They are so perfect, fiery with Kashmiri chillies but not searingly hot, cooked medium rare in the Tandoor and there’s a flavour I like but can’t identify. Research reveals it’s Nagercoil clove, a highly aromatic clove from the Nagercoil region. We chew the chops down to the bone, narrowly missing our fingers in our ecstasy.

These are all ‘starters’, but we are starting to feel a bit full. All the same, a ‘Somerset Lamb’ biryani cracked open at table releases such incredible steam-driven aromas we easily get a second wind.

Best biryani ever. The rice is perfect ‘witches fingers’ showing the quality of the rice and the precision of the cooking. It’s light and packed with flavour and the meat fall apart tender. A good biryani is no easy thing, but this is better than good.

The only dish I don’t rave over is the Chicken Makhani – chargrilled chicken in creamed tomato with fenugreek leaves – and this is my fault, I forgot that I have always found this dish too sweet for my taste. That said, the other side of the table loves it and she takes care of the dish for me.

With the mains we eat delicate naans, a superbly rich and creamy black dal and a dish of lightly fried potatoes. The Dal does me in, it’s a Mr Creosote moment.

Still we have to do our duty and so do dessert. We share a plate of samples: Raspberry & cardamom cheesecake, ‘Chocolate delight, almond brittle, caramel ice cream, and a medley of kulfis – Salted caramel, rose malai, pistachio  – and a Calamansi posset, cranberry compote with mini rasgulla .

Some real delights in there, the Raspberry & cardamom cheesecake particularly fine.

We apologise to our lovely waiters for not doing the desserts justice and they understand, having seen just how much we’d already eaten.

Then it’s the climb back up those stairs, which seem to have increased in angle since we came down them earlier.

Dragging ourselves up like two exhausted mountaineers we finally reach the outside world elated and sated and singing Kahani’s praises.

1 Wilbraham Place