Her doctors have said she is making a good recovery.

The 90-minute operation was carried out yesterday afternoon at King Edward VII Hospital where she has had treatment before.

News of the surgery, which had been planned for some time, came in a Buckingham Palace statement on Thursday afternoon.

The Queen Mother is expected to remain in hospital for about two weeks.

In recent months it has been noticeable that she has been in considerable pain and has often been driven around in an electric buggy on royal engagements.

Last week she leant heavily on two walking sticks at a Remembrance Day service.

At 95, the Queen Mother is one of the oldest people ever to undergo a hip replacement which is considered risky for someone of her age.

The Queen is reported to have expressed worries about the danger to her mother but was reassured by the Queen's Physician, Dr Richard Thompson.

The surgery was carried out by the Queen Mother's personal orthopaedic specialist Roger Vickers who was assisted by hip replacement specialist, William Muirhead-Allwood.

It may take the Queen Mother some time to recover from the surgery and it could be up to three months before she can walk unassisted.

About 50,000 hip replacements are carried out each year on the NHS.

However, they are rarely performed on patients over the age of 75, partly because of the risks but also because the procedure costs an average of �3,500.

The operation was pioneered in the 1950s but did not become routine in Britain until the 1970s.

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