When Richard and Antony Joseph were schoolboys, their father Michael gave them a holiday job. He needed extra pairs of hands at his industrial glass factory in Birmingham. And so his twin sons found themselves shovelling broken glass during the summer vacation. “Our dad would sell it to us like it was the best job in the world,” Richard says cheerfully. “But we’d be there with blisters.”

The hard work was good training. Within a decade, the 37-year-old designers-turned-entrepreneurs have built Joseph Joseph, their kitchenware company, into a business with a turnover of ￡22.5m in 2011, up from ￡12.5m in 2010. On a recent spring evening at their London headquarters, a cool space swathed in the most modern of corporate greys, the rest of the staff are drifting home for the evening as the brothers chat in the boardroom, their phones buzzing with calls.

They are gracious and at ease but is it really that easy? No, they admit. On the business front, there is the vastly expensive copyright wrangle they have just won after a hard fight in China; and on a personal level, when the subject of sibling arguments comes up, Antony laughs darkly about the time he threw a pile of books at his brother’s head in the boardroom. “They clipped the ear of our non-exec chairman [Roger Crudgington] instead,” he says.