When the doors of the Fountain Restaurant – Fortnum & Mason’s sexagenarian restaurant – closed for the last time in 2015, there were some quiet grumblings from its loyal clientele of scone scoffers and tea drinkers. It was time, however, for a change. Enter 45 Jermyn St. – a restaurant and cocktail bar that faced up to the challenge of combining the charm of its traditional surroundings with the excitement and innovation of London’s food scene.

Gone are the tasteful pastels and ornamental tea-sets of the Fountain’s yesteryear. 45 Jermyn St., by comparison, is a bright and bold nod to the mothership. Fortnum’s now-iconic pistachio walls and cream ceilings presented the perfect backdrop to a set of bright burnt orange leather chairs and banquettes that punctuate and snake across the centre of the dining room. Throw in a parquet floor, mottled marble bar, brass accents and 113 hungry diners, and you’ve got yourself a modern and vibrant stage upon which the food and drink better measure up.

The restaurant is open throughout the day, serving breakfast, lunch, dinner and a late night supper menu. It’s early afternoon when we shuffle to our table and take the only two seats left in the house. Once ensconced and served with a glass of fizzy water, we’re left to peruse the menu – and then to our own devices. My friend checks her phone. I check out our fellow diners: well dressed (it is Jermyn Street), well spoken (‘’I hold James in the highest regard”), and well fed (as I soon hoped to be).

For our starters, we eschew the oysters and caviar trolley (though it does present quite the spectacle with baked potatoes and scrambled eggs cooked on demand, and garnished with Iranian Beluga, Golden Oscietra or Siberian Sturgeon roe served by the gram). Instead, we opt for the octopus with braised borlotti beans and chorizo, and a half moon of meaty Dorset blue lobster and crisp Russian salad of carrot and green beans. While the octopus is well seasoned, there could be more sublime discs of tentacle and sausage for our liking.

On the advice of Wesley, our newly-introduced gastronomic aide-de-camp, for mains we go for the Glenarm Estate rib steak with Café de Paris butter (“it’s got more than 20 ingredients”). The meat, which is the size of my hand, arrives cooked to order topped with a circle of tangy butter that melts and melds to each exquisite mouthful. All was washed down with a glass of 2013 Lytton Springs red – a wine from the Californian Ridge Vineyards and the perfect accompaniment.

Little time to chat, we were too busy swooning over a plate with a bevy of plump Beesands scallops served on a choppy bed of chorizo pieces and smashed up neeps, and duly quaffed with an Alsatian pinot gris “A360P” grand cru Muenchberg (“to complement the flavours of the sea”).

Once sufficiently recovered, we were presented with the ‘Afters’ menu. A small selection of sweet or savoury delicacies this was not – we oh-so-bravely steeled ourselves for a real dessert. A rich plug of chocolate mousse adorned with a quenelle of mint ice cream was almost too much, while we dutifully waded spoon deep through a fluffy Grand Marnier soufflé.

It’s a pity that we didn’t have the room or the courage to explore the menu further – a boozy cognac and strawberry float spiked with citrus and knobbly peanut butter or cherries soaked in brandy with vanilla ice cream would’ve gone down a treat. And we made nary a glance at the cheese. Not to worry – on the list for next time. Something tells me 45 Jermyn St. is going to be around for a while.