Leading members of the Royal Family are playing key roles in this weekend's Trafalgar bicentenary celebrations.
The Queen and Prince of Wales were among those who lit beacons to mark the 200th anniversary of the sea battle and the death of Lord Nelson.
More than 1,000 other beacons were lit around the country during the evening of Trafalgar Day on Friday.
Organisers estimate there will be more than 6,000 events in all during the Trafalgar weekend.
1845 BST HMS Victory, Portsmouth
1848 Ballater, Aberdeenshire
1850 Killyleagh, Co Down, Northern Ireland
1852 HMS Cambria, south Wales
1858 RN College, Greenwich, south London
1859 - Other Portsmouth beacons
1900 - Burnham Thorpe, Norfolk
1915 - All other beacons
Fry-ups to fireworks
The national beacon at Portsmouth and principal beacons - in northern Scotland, south Wales, County Down in Northern Ireland and London - were lit in sequence by members of the Royal Family.
They were followed by one at Nelson's home town of Burnham Thorpe, in Norfolk, and then more than 1,000 around the country.
Other events over the Trafalgar weekend include cooked breakfasts, lunches and dinners in honour of Britain's battle success, fireworks parties and church services.
There are also plans to create a peal of bells across the country on Sunday evening.
Bruno Peek, head of the organising body, Trafalgar Weekend, said before the event: "We are delighted that the Royal Family has agreed to commemorate Nelson and his brave crews in this unique way."
His team has spent more than two years co-ordinating the formal weekend celebrations, which follow a number of sea-based events during the summer.
And he says that there will be hundreds of private events as well as those formally registered with his organisation.
"We have just over 800 beacon-lightings registered at the moment, and we expect more," said Mr Peek. "But there will be many more who won't be registering because they are not open to the public.
"In total, I reckon there will be over 6,000 events including bell-ringing, lunches, parties, dinners, and so on."
Each nation had one of the principal beacons, which were lit in between the two English ones - beside Nelson's flagship, HMS Victory, in Portsmouth, and the Royal Naval College at Greenwich, where Nelson's body lay in state before his funeral.
The Queen was at Portsmouth Historic Dockyard to light the first beacon at 1845; the Prince of Wales was at Ballater, in Aberdeenshire; the Princess Royal at the Royal Naval Reserve base at HMS Cambria, in south Wales, and the Duke of York at Greenwich, and Prince Edward was at in Killyleagh in Northern Ireland,
1845 BST - HMS Victory, Portsmouth Historic Dockyard.
The Queen lit the national beacon alongside Nelson's flagship. Unsurprisingly, Portsmouth is the focus of a number of Trafalgar celebrations, marking the city's strong links with Nelson. Other Portsmouth beacons were lit at 1859 BST, shortly after the last of the "royal" beacons.
1848 BST - Church Green, Ballater, Aberdeenshire.
Prince Charles lights the first of the so-called principal beacons not far from Balmoral on Royal Deeside. Scotland was the site of the first UK monument to Nelson following his death.
1850 BST - Killyleagh, County Down.
Prince Edward lit the principal beacon. About one-third of the men who sailed with the British fleet came from the island of Ireland.
1852 BST - HMS Cambria, south Wales.
The Princess Royal did the honours at the Royal Naval Reserve base near Barry, where there is a model of the signal mast displaying Nelson's famous "England expects..." message.
1858 BST - Royal Naval College, Greenwich, south London.
The Duke of York lit the final principal beacon outside the Painted Hall, where Nelson lay in state before his body was taken by barge along the Thames to St Paul's Cathedral for his burial.
Note: most of the events are private - only a few are open to the public. More details are on the Trafalgar Weekend website.