At 52, Mr Tyrrell is only a few years younger than Mr Birch, who is nearly 56. Senior management changes last September made it clear that the next chief executive is more likely to emerge from a group of younger candidates including Ian Harley, who will replace Mr Tyrrell as finance director from next week.
Mr Tyrrell is moving to take over as finance director of London International Group, best known as the maker of Durex contraceptives. Paul Rew, LIG's company secretary, said he did not know whether Mr Tyrrell had been promised a chance to succeed Tony Butterworth as LIG's chief executive. Mr Butterworth is about the same age as Mr Birch.
Mr Tyrrell was on his way to Manchester for a board meeting at Boddington, the pubs group where he is a director, and could not be contacted for comment.
He was managing director of HMV Shops at Thorn EMI before joining Abbey National in 1982, when the lender was still a building society owned by its depositors and savers. He joined Abbey National's board four years ago.
David Harbut, LIG's present finance director, is retiring at the end of next month and Mr Tyrrell will take over in July.
LIG was recently in trouble with the Stock Exchange after it briefed 13 analysts and four of its largest shareholders to lower their expectations of profits. Mr Rew said Mr Tyrrell's appointment was totally unconnected with this criticism.
'We are very pleased to get someone who has so much experience of plc directorship as James Tyrrell and so much experience of relations with the City,' Mr Rew said.
John Fry, Abbey National's group services director, dismissed suggestions of a row between Mr Tyrrell and his colleagues, saying: 'We are the best of friends and we think and work the same way.'
Mr Tyrrell did not have a service contract but is expected to receive some compensation for loss of office.
Besides Mr Harley, who is 42, Abbey National's high-fliers include Gareth Jones, director of retail operations, Charles Toner, 51, managing director, new business, and Bob Knighton, information technology director.
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