HRH Queen Mary invited Madge Watt, who found the first WI in Great Britain, to form a WI at Sandringham, and the Queen became its President.
This tradition was followed by future members of the Royal family.
HM Queen Elizabeth II became a WI member in 1943 when she was still Princess Elizabeth; her Mother was President of Sandringham WI.
Her Majesty The Queen is still President of Sandringham WI. HRH
The Countess of Wessex is a member of Bagshot WI, Surrey.
HRH The Duchess of Cornwall is a member of Tetbury WI, Gloucestershire.
HRH Princess Anne is an Associate Member.
A speech by The Queen at the Sandringham Women's Institute, 2009
The Queen's Speech - Women's Institute Centenary Annual Meeting