Touker Suleyman became a Dragon after joining the regular Dragons' Den panel in series 13.
Suleyman is a British-Cypriot entrepreneur and investor best known for businesses in fashion and retail. He joined the British programme during its thirteenth series, adding experience from clothing manufacturing, brands and consumer products to the investor panel.
His arrival followed a period of turnover among the Dragons, when the programme refreshed its lineup rather than keeping every earlier investor. Suleyman's investment interests have included fashion companies and other consumer-facing businesses, making him a particularly relevant Dragon for pitches involving retail, licensing and product development.
Series numbers are more reliable than informal descriptions such as “the mid-2010s,” because several investor changes occurred close together. This answer should not be confused with James Caan or Nick Jenkins, who were also Dragons but belonged to different panel eras.