On Thursday the Queen took part in a walkabout where she was greeted by thousands of adoring fans, who had lined the streets of Windsor to wish Her Majesty a very happy 90th birthday. Her second public appearance of the day was no different, as the monarch was met by the sound of rapturous cheers and applause.
The Queen was attending a beacon lighting ceremony, also in Windsor. She was accompanied by her husband Prince Philip, who turns 95 this year, her son Prince Charles and Charles' wife the Duchess of Cornwall at the evening engagement.
The royal birthday girl lit the principal beacon, which set in train a series of over 1,000 beacons across the country and worldwide.
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The Queen was accompanied by Prince Philip, Prince Charles and the Duchess of Cornwall
Beacons large and small will be lit to mark the Queen's 90th, and members of the public have been asked to attend a beacon-lighting event in their area, hosted by their local authority.
Members of the Army Cadet Force have also taken beacons to the top of the four highest peaks in the UK – Ben Nevil, Scotland; Mount Snowdon, Wales; Scafell Pike, England and Slieve Donard, Northern Ireland.
The Queen wore the same spring green coat by Angela Kelly that she had debuted earlier in the day, but swapped the matching hat for a headscarf for the evening ceremony.
The Prince greeted his 'mummy' as she arrived for the ceremony
Following the short engagement, the Queen headed home to Windsor Castle, where she is believed to be having a private dinner with 71 guests, including 30 members of the royal family – and will no doubt be treated to more birthday cake.
The celebrations won't stop there though. On Friday the Queen will host US President Barack Obama and First Lady Michelle for a private luncheon at Windsor Castle.
In May, four nights of celebrations will be held in the grounds of the Berkshire royal residence. The final evening will see Katherine Jenkins, Kylie Minogue, Jess Glynne and other performers participate in the event. It will be hosted by Ant and Dec and broadcast live by ITV.
In June, as well as the traditional Trooping the Colour ceremony, the Patron's Lunch, which has been dubbed "the nation's biggest street party", will be held on the Mall for 10,000 guests.