Mr O'Donnell, a top flight economist, is to become the head of the Treasury's monetary group - handling interest and exchange rates - in what Whitehall officials were at pains to emphasise was a conventional civil service career move. Mr O'Donnell, quietly spoken and well-liked in Whitehall, has nevertheless had one of the most difficult periods in the job of any recent press secretary.
The appointment of Mr Meyer, a Foreign Office high-flyer who was head of its news department under Lord Howe, means that Mr Major has opted for another career civil servant.
Mr Meyer, an urbane linguist and Russia expert, became well- known to journalists in his time as Lord Howe's spokesman for 'double act' briefings with Mr O'Donnell's predecessor Sir Bernard Ingham at international summits. Mr Meyer, who was educated at Peterhouse College, Cambridge, and spent a year at Harvard before joining the British embassy, where he is said to have impressed American officials with his grasp of adminstration policy under both Presidents Bush and Reagan.
Although he has little experience of domestic policy issues he was admired in the civil service for handling the steadily deteriorating relations between Baroness Thatcher and Lord Howe.
His next post would have been as an ambassador if he had not been chosen for the Downing Street job.
Mr O'Donnell, who has to cope with an unprecedented barrage of critisism of Mr Major from the normally friendly Conservative press - notably during the Prime Minister's recent trip to Tokyo - has told friends that he sees his departure as 'bittersweet'.
Mr O'Donnell, 41, had intended to return to the Treasury before the next general election though there were signs that the timing of the announcement might have been influenced by the strong personal backing for the Prime Minister at the Conservative Party conference.