Queen Elizabeth Is 'in Great Spirits' as She Makes Surprise Appearance at Windsor Horse Show

Queen Elizabeth made a surprise appearance among the crowds at the Windsor Horse Show on Friday.

The monarch, 96, was driven the short distance from her Windsor Castle home to see three of her fell ponies take part in the race. She watched the event from the comfort of her Range Rover — and was overjoyed to see one of them, Balmoral Leia, win the Highland Class.

The Queen, who missed the State Opening of Parliament on Tuesday due to "episodic mobility problems," was all smiles during the outing. Dressed in a sweater and collared shirt, she also sported her bright pink lipstick.

"She was in great spirits," an observer tells PEOPLE. "People she knows in the horse world were being brought to her to talk to her at the window. You can see she is in really good form."

James Whatling/MEGA Queen Elizabeth

Later in the morning, she was driven to the main arena and was seen walking slowly to a lift, aided by a walking stick. She then made her way to her seat, which was next to her son Prince Edward in the stands.

RELATED: Queen Elizabeth and Prince Philip's Untold Love Story: 'She Never Looked at Anyone Else'

James Whatling/MEGA Queen Elizabeth

And she got a special treat when her great-granddaughter Lady Louise Windsor rode by in the saddle of the Queen's beloved late husband Prince Philip's carriage as she led a parade through the arena.

PA Images/Alamy Stock Photo Queen Elizabeth

The Queen's public life has been curtailed by recent health issues recently. She has been experiencing mobility issues in recent months and finds it difficult to stand for long periods. Her Majesty has been using a walking cane and even complained about mobility problems, joking during an in-person meeting: "Well, as you can see, I can't move!"

Tim Rooke/Shutterstock Queen Elizabeth

It is the first time she has been seen in public since she attended the Thanksgiving Service for her beloved late husband Prince Philip on March 29.

Tim Rooke/Shutterstock Queen Elizabeth and Prince Edward

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The Windsor Horse Show is one of the Queen's favorite annual events. As it takes place near her castle home, she typically attends.

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In honor of the Queen's 96th birthday last month, a new portrait of the monarch was released by the Royal Windsor Horse Show.

The majestic shot, which was taken on the grounds of Windsor Castle, shows the Queen standing proudly between two of her fell ponies, Bybeck Katie and Bybeck Nightingale. She wears a dark green cape-style coat as she holds the reins of two of her favorite ponies in front of a magnolia tree.

henry dallal photography Queen Elizabeth

Throughout her life, Queen Elizabeth has always had a fondness for horses and was given her first horse (a Shetland pony) when she was just 4 years old. She's also been known to get animated at horse racing events, enthusiastically cheering for her horses.

However, she reportedly hasn't ridden since early September due to mobility issues.

The Queen's birthday will be officially celebrated next month during the Platinum Jubilee celebrations, which includes her annual birthday parade, Trooping the Colour. The long weekend of events will see the royal family, including Prince Harry and Meghan Markle, gather to honor the monarch's historic 70 years on the throne.