One Group commercial director (Europe) Jon Yantin is leaving the company after six years in the role, "to pursue new opportunities".
Yantin's departure comes as the New York-based hospitality group, led by UK entrepreneur Jonathon Segal, continues its drive into the UK and Europe after raising $15.5m (£9m) to fund restaurant growth following its public listing in the US in 2013.
Chief executive officer Segal praised Yantin's contribution to the group. Yantin was a member of the senior leadership team that launched the business in Europe. Segal said: "Jon has made a significant contribution to the development of our business in Europe. As the company evolves, I would like to thank him and to wish him well for the future. Adam Elliott continues to lead our growth in EMEA as our European chief operating officer."
One Group said Elliott will oversee Yantin's responsibilities "for the time being", including all development and site expansion plans.
It is unclear where Yantin, who relaunched the Chicago Rib Shack in Knightsbridge in 2005, after raising £3m in funding, is headed next.
The One Group is targeting the UK as a key part of its expansion plans. In November last year it announced plans to open its first standalone restaurant in Europe. At the time the group said it would be one of a new casual-dining concept called STK Rebel in Edinburgh's South St Andrew Square development in 2017. The company has since shelved plan for the new brand, and said that the site will now trade as an STK restaurant.
It is also in talks to open a site Manchester, which had been lined up as being an STK Rebel, but is now likely to be an STK branded site.
The One Group also plans to open two more of its flagship STK brand steak restaurants in London and has recently expanded into Europe after signing its first franchise agreement which will see an STK open in Ibiza later this year.
Its first move outside the US saw One Group open STK London in 2012 in the five-star ME London hotel on the Strand, as part of a hospitality deal with the hotel's owners to run all of the food and beverage operations.
It also runs the Cucina Asellina, Radio rooftop bar and Marconi Lounge within the same hotel, as well as managing the hotel's banqueting and room service operations. The group also runs the Heliot steak house at the Hippodrome casino in London's Leicester Square.
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