In a nutshell: Sloane Street's new luxury restaurant stakes a bold claim to being "Italian-Japanese".

The welcome: Reservations are basically the law at Sumosan Twiga - anything new on fashionable Sloane Street is going to turn the heads of the area's social elite. And duly, a cluster of receptionists are on hand to walk well-dressed internationals and on-the-pulse locals up a glamorous Georgian stairwell, to the first floor dining room and second floor bar.

The space: The two rooms are largely the same style - relaxed, well polished, but rather anonymous. The main difference is the white colour palette in the dining room, and darker hues upstairs. Guests are encouraged to put on their dancing shoes in the dining room later at night, while the bar is more for chewing the fat over business deals with a negroni.

Food and drink: The Italian-Japanese concept is clearly a stretch, so much so that attempts to justify it rather than just admit it is to get bums on seats are futile.

But look past the culturally weird menu, and you're encouraged to pick from the a La Carte serving classics from both cultures (edamame, gyoza, ragu, mozzarella, sushi, sashimi) which stake their claim against new-world dishes served with more opulent finishing touches (black cod with miso, truffle hamachi tiradito).

Given that people aren't going to Sumosan Twiga for the food (this is ultimately a socialising spot) we were glad that some of the dishes passed with flying colours.

The star attraction as recommended by knowledgeable staff was the black cod miso, a shareable glazed icon dish with a divinely rich, syrup-like miso exterior that was almost unnervingly perfect - an ode to Nobu's original dish. That rich glaze never sacrifices the cod's own unique robustness.

Other fine turns included a simple pasta ragu, served home-style, plated in front of customers in the restaurant, which our Italian guest craved more of. Lightly fried gyoza had a tangy, certainly home-made sauce to pair and retained a pillow softness that requires careful attention, and the Italian gelato both summed up Sumosan's talent at getting dishes to look good, and taste good too.

But these were the star attractions - other dishes felt tired and uninspired. Sashimi and sushi looked and tasted dried out, there was an abundance of truffle where truffle wasn't needed (including in unnecessary theatrical circles on bits of sashimi), and home cooking staples like Vitello Tonnato looked frumpy and simply didn't suit the restaurant's aesthetic.

A general tendency to be too ambitious with the menu has hampered real concentration on flavour.

Would we return?This fine but forgettable melange of cuisines has no distinct hallmark.