Millions of scouts, old and young, are celebrating 100 years of the movement. It was founded by British Army officer Robert Baden-Powell.
Hundreds of scouts from 160 countries gathered at Brownsea Island in Poole Harbour, Dorset, the site of the first camp organised by Lord Baden-Powell in 1907.
Chief Scout and former Blue Peter presenter Peter Duncan led a special ceremony on Brownsea. He blew the original kudu horn that Lord Baden-Powell used to start the first camp.
Young scouts from all over the world represented their countries at the Brownsea gathering. This Israeli girl was one of those chosen to attend.
British scout, Alastair Frankl, 16, read out Lord Baden-Powell's speech of 100 years ago. Later, scouts took part in a range of activities including Tai Chi.
Elsewhere in the UK, 40,000 scouts have gathered for a 12-day jamboree near Chelmsford, Essex. The event in Hylands Park was opened on Saturday by Prince William.
Despite festivities lasting late into the night, the scouts in Essex were up with the larks for a sunrise ceremony to mark the centenary.
Throughout different time zones, they renewed their promise at exactly the same moment. Brownsea Island and Essex were linked up by satellite to share the experience.
Afterwards they collected signatures on their "sunrise" scarves. In total, there are believed to be 28 million scouts worldwide.
Hundreds of scouts also walked around Stonehenge in Wiltshire to renew their promise. They vowed to help others and do to their duty to God and the Queen.
Celebrations were held as far afield as Namibia and Ecuador. In the German town of Langenlonsheim, scouts took part in an early morning candlelight vigil.