New Delhi, June 20 -- If Indian business history were a story, Lalit Mohan Thapar would emerge as one of its more intriguing characters.

Not so much a founder, an uber-billionaire or a visionary, he was the custodian of an old commodity-and-engineering business that strugged to change even as India transitioned from license-raj to a more competitive economy.

Born in 1930 to industrialist Karam Chand Thapar, who had moved from Punjab to Calcutta in 1920 to build a coal-trading business, LM Thapar inherited a group whose interests already stretched across coal, jute, textiles, paper, engineering, banking and insurance.

Educated at Doon School and the University of Southern California, where he trained as an engineer, Thapar took charge o...