For nearly two decades, Sir Denis Rooke was the towering force in the UK gas industry, transforming an ageing public sector utility based on Victorian technology into one of the world's largest private sector energy corporations.

A strikingly tall figure with a jutting profile, Sir Denis, who died this week at the age of 84, was the unmistakable embodiment of British Gas and impetus behind this transformation. His influence was often compared with his appearance: powerful, even intimidating. He drove through changes at British Gas with a single-mindedness of purpose, a concern for engineering excellence and a deep sense of public mission.