Antonio Vigorito's new cocktail menu features three categories of drinks with titles reflecting the number of calories they contain.
Drinkers can choose from low-calorie non-alcoholic cocktails (The Saintly), higher calorie alcoholic cocktails (The Sinful) or more indulgent alcoholic cocktails (The Wickedly Good). The number of calories contained in the cocktails ranges from 34 for The Stressbuster and Sweet Gingerol to 270 for Eye Candy.
Vigorito told BigHospitality he'd come up with the idea having noticed that the public were becoming increasingly concerned with their health and weight. Also, despite many restaurants now putting calorie counts on menus, the practice is not yet one seen in the bar sector.
He said: "I did quite a bit of research when I came up with the idea and couldn't find anyone else doing this. People are more knowledgeable about the food and drink they are consuming these days, they look at the labels more and are interested in the calorie content of each thing which was the main reason for me doing this.
"It's been really interesting to see in this past week. Lots of people, mostly my female customers, are choosing cocktails now based on the calories they contain. In my experience the men go for flavour rather than the calories. Since the launch I have also noticed that we are getting new customers in who have been at gyms in the area and have heard about our menu."
The mixologist, who worked with a team of nutritionists to work out the calorie count of each cocktail he serves, has also used the exercise to re-think the ingredients that go into them.
"I'm now using less syrups and sugary liqueurs in my cocktails and replacing them with fresh fruit," he said. "It was a suggestion from the nutritionists. When I gave them a recipe for a cocktail with ginger ale in it for example they came back and said, why didn't I use fresh ginger and soda water instead?"
Vigorito, who now makes most of his ingredients from scratch and is using more organic products, said the practice took more time, but the cost was the same.
"It's been an amazing experience to work with the nutritionists. It takes a little more time to make things up, but I'm enjoying making drinks that concentrate on the flavours of the ingredients and alcohol involved and that don't need lots of sugar to make them taste good," he said.
The launch of the cocktail menu coincided with a re-design of Rockwell restaurant and bar, part of Hilton's Trafalgar Square hotel, The Trafalgar. The new interior features dark wood, light grey and brushed metal with and lime coloured leather armchairs and black velvet chairs.