Lord White, the strategist who built up Hanson and chaired the American interests over more than 20 years, was last night seriously ill in a Los Angeles hospital.
He has been taking a back seat for some time at the pounds 14bn Anglo-American conglomerate, leaving much of the day-to- day running to his long-time colleague, David Clarke.
Mr Clarke was always viewed at Lord White's heir, but that succession was thrown into confusion earlier this year.
Mr Clarke is now off to run the group of US companies being de-merged by Hanson, and he will be replaced by the company's finance director, William Landuyt, aged 36.
The departure of Mr Clarke, and the realisation that Lord White may not continue working at the company even if he recovers, may cause concern about the impact of losing two such figures at the same time.
Nevertheless, Mr Landuyt, who is American and used to work at the US operations, is seen as the archetypal Hanson executive and is generally regarded as Lord White's successor.
Earlier this year, Lord White was extolling the strength and depth of Hanson's management, which allowed executives to be moved to and from senior positions without disruption to the organisation.
In the UK, the promotion of Derek Bonham from finance director to chief executive three years ago was seen as an attempt to stem City criticism that Lord Hanson lacked an heir-apparent.
His appointment was significant in that it separated the roles of chairman and chief executive. The move also skipped a generation, indicating that Lord Hanson realised the urgent need for younger blood to come forward.
Hanson's pounds 2.5bn offer this week for Eastern Group is widely viewed as Mr Bonham's deal, and so long as there are no big problems the takeover should secure his position as the company's future head and top deal-maker.
He is said to get on well with Mr Landuyt, and the latter's knowledge of the businesses on both sides of the Atlantic should enable them to work as a team.
However, the Hanson duo is regarded as unique, with Lord White planning the deals and Lord Hanson acting as the administrative brain that saw them through. Neither is due to retire officially until 1997.