The £1m boat that will the lead the Thames Diamond Jubilee Pageant has been launched on the river.
The 94ft (28.6m) royal barge Gloriana was escorted through the streets of London on the back of a truck.
It had been transported from a unit in Brentford to Isleworth, west London, where it was placed in the Thames.
A pageant of more than 1,000 boats involving some 20,000 people will sail down the river on 3 June to mark the Queen's 60 years on the throne.
The Queen will formally name the barge when she visits Greenwich next week to unveil the revamped Cutty Sark.
The pageant, from Wandsworth to Tower Bridge, will be led by Gloriana, a rowbarge which will be powered by 18 oarsmen.
It will feature a seven-mile long procession of Dunkirk little ships, historic vessels, steam boats and tugs.
The Gloriana, which is covered in gold leaf, will not carry any member of the Royal Family.
Lord Sterling, who organised Jubilee celebrations in 2002, is behind the project which created the barge.
He said the idea for a waterborne tribute to the Queen came from Prince of Wales and the vessel featured wood from sweet chestnut trees grown on Prince Charles's private estate.
Lord Sterling said: "I became enamoured with the idea of building something timeless and got inspiration from Canaletto's paintings that showed the great barges of the 18th Century and decided to build one.
"If we had to give it a style, it would be Regency. Including 18 rowers, it will carry 52 people.
"No-one's really built anything like this for 200 years and the way we've built it, it will last for 200 years if looked after.
"This has been a huge project. Something of this type would normally take a year or so to do it but we've done it in far less."
The team behind building the vessel, led by master-builder Mark Edwards, had been working 18-hour days to complete the project, which began last November.
Music is a key feature of the celebrations, with pieces commissioned for the pageant receiving their premiere on special musical barges.
Carol Ann Duffy, the poet laureate, has written the words for a new song with music by composer Orlando Gough.
Ten film composers, including Downton Abbey composer John Lunn, were commissioned to devise a new movement inspired by the original titles of Handel's Water Music.
The flotilla will feature 20,000 people on the water, travel under 14 bridges and take 90 minutes to pass any given point.