STORY: Elizabeth, 96, missed the grand set-piece ceremony at parliament on Tuesday (May 12) because of what Buckingham Palace described as "episodic mobility problems".
She has rarely been seen in public since being hospitalised for a night last October for an unspecified illness, and then being told by her doctors to rest. She has since carried out duties either remotely or in person at her Windsor Castle home.
But on Friday, she was pictured smiling happily from the front passenger seat of her Range Rover car as she watched some of her horses compete at the Royal Windsor Horse Show, which is taking place in the private grounds of her castle.
She later took her seat in the stands to applause from the crowd, walking with the aid of a stick.
The four days of events at Windsor that started on Thursday include "A Gallop Through History", which features more than 500 horses and 1000 performers and is designed as a tribute to the queen's 70 years on the throne.
The finale is on Sunday (May 15), when the queen is expected to attend, with actors Tom Cruise and Helen Mirren among the British and international stars who will be taking part.
It kicks off celebrations to mark her Platinum Jubilee which will culminate in four days of national events from June 2.