Day promoted Simpson to deputy chief executive of British Aerospace in December 1991 to "toughen up" the company's management.
He had been part of negotiations which would have seen Honda increase their 20% share in Rover to 47.5% with the aim for a stock market flotation.
GEC favours forging a national 'champion' defence group with BAe to compete with the giant US organisations."
Marconi borrowed heavily to finance expansion into this market and was especially vulnerable to the burst of the dot-com bubble.
After a "botched" profits warning in July 2001 Simpson's deputy chief executive, John Mayo, resigned.