Official events to mark Her Majesty's milestone birthday began in earnest with visits to the Royal Mail and Alexandra Gardens in Windsor
The day began with the release of a commemorative photograph from an institution which also celebrates a big birthday this year: the Royal Mail, which turns 500 this year.
The Queen marked the joint birthdays with a visit to the Royal Mail delivery office in Windsor where she met long-serving staff and learnt more about the organisation's daily operations.
Her Majesty was treated to what is likely to be the first of many rousing choruses of 'Happy Birthday' this year.
The Queen and The Duke of Edinburgh went on to Alexandra Gardens where Her Majesty opened the new Bandstand. Her Majesty and His Royal Highness met school children from the six schools involved in the bandstand's decoration before a children’s choir will performed four short songs followed by a performance of Shakespeare as part of the School's Shakespeare Festival.
Celebrations will continue on Her Majesty's actually birthday on 21 April, and in June, when she marks her official birthday.