A national service of thanksgiving at St Paul's Cathedral honours the Queen's "faithful devotion" through times of "turmoil and change" on her 90th birthday.
The Queen lights the first of more than 900 beacons being lit across the UK and overseas, as part of her 90th birthday celebrations.
Test your knowledge of some lesser-known facts.
The flames, the crowds, the guns - as Queen turns 90.
What can we learn about longevity from the Queen?