Ethan Koh is a fourth-generation descendant of the Singaporean family behind Heng Long Leather—a tannery for exotic skins which supplies some of the world’s top luxury brands. Koh founded Ethan K in 2009 as a maker of vibrant bespoke crocodile skin handbags, which proved popular with royals. He told Alexandra Newlove about capturing the millennial imagination, his most unusual bespoke requests, and his advice for the next generation looking to make their mark