Britain's Queen Elizabeth II reacts as she tours the Royal Mail Windsor postal delivery office in Windsor, west of London, on April 20, 2016, to mark the 500th anniversary of the Postal Service. Queen Elizabeth II is set to celebrate her 90th birthday on April 21, with a family gathering and a cake baked by a reality television star, as a new poll finds Britain's longest serving monarch is as popular as ever. The queen has reigned for more than 63 years and shows no sign of retiring, even if she has in recent years passed on some of her duties to the younger royals. / AFP PHOTO / POOL / Chris Jackson