An estimated 1 million people are expected to line the river's banks from Putney to Tower Bridge as boats accompany a specially designed barge bearing the queen's party
Queen Elizabeth diamond jubilee fete with a girl's best friends
LONDON // Starting today, millions of Britons will throw themselves into four days of national celebrations - some very formal, but most not - to mark Queen Elizabeth's 60 years on the throne.
But at least two people attending the events might well be secretly hoping things do not go entirely to plan: the queen herself and her husband, the Duke of Edinburgh.
"One of the things I know that over the years, they've loved it when things go wrong," Prince William, the couple's grandson and second in line to the throne, reveals in a television documentary aired late last night in Britain. "They absolutely adore it because, obviously, everything always has to be right. But when things go wrong around them, they're the first people to laugh. The queen has seen so many parades or performances, when there's a small slip-up it tickles their humour."
Even the queen, though, is unlikely to have seen anything like the centrepiece of the weekend's celebrations tomorrow when 1,000 private boats from all over the Commonwealth take part in a pageant along the River Thames through London.
An estimated 1 million people are expected to line the river's banks from Putney to Tower Bridge as boats from historic sailing ships to kayaks accompany a specially designed barge bearing the queen's party.
On Monday, in the grounds of Buckingham Palace, there will a diamond jubilee concert, which the BBC will broadcast around the world. Paul McCartney, Elton John, Tom Jones and Stevie Wonder are among a host of legends from the world of music, dance and musical theatre who will be performing.
And on Tuesday, the final day of the diamond jubilee national holiday, the queen will attend a special service of thanksgiving at St Paul's Cathedral and then a formal royal carriage procession from Westminster to Buckingham Palace along a route expected to be lined by thousands of well-wishers.
However, given her lifelong love of horses, the 86-year-old monarch will probably derive most pleasure from her one engagement today - her attendance at Epson racecourse for the running of the Derby, which is expected to attract a record crowd of 200,000.
Across the country, meanwhile, literally tens of thousands of events will be going on, from street parties to village picnics, funfairs to firework displays. For those with more bizarre tastes, there will be kilt races in Perth, coronation chicken-flavoured ice cream tastings in Soho, and frozen sausage throwing competitions in Northumberland.
More than 9,500 road closures, 4,000 more than for last year's royal wedding between Prince William and Kate Middleton, have been approved by local authorities in England and Wales for street parties over the weekend, many of them with a 1950s theme.
Flick Rea, the chairwoman of the of the Local Government Association's culture and tourism board, said: "It's the beginning of a summer of celebration. There's a huge respect for the queen and, with the fever around the Olympics and the weather, we're now celebrating.
"I think when you're living in hard times, people like something to take themselves out of it. Just to get out on the street with people makes a huge amount of difference - you need your neighbours when times are hard."
Fewer street parties are planned in Scotland and Northern Ireland, which do not share the tradition dating back in England and Wales to the end of the First World War, but scores of other events, including barbecues and music events, are on the cards.
The comedian Des Clarke told the Edinburgh Evening News: "The relationship between Scotland and the Queen is quite interesting. Will we be having lots of street parties? No. Are we glad we're getting a couple of days off work? Yes."
Across the whole of the United Kingdom, though - from Land's End to the Orkney Islands, and from the Channel Islands to the Outer Hebrides - more than 4,000 beacons will be lit on Monday night to mark the jubilee.
The last beacon will be lit by the queen after the Buckingham Palace concert. She will walk out in front of the 20,000-plus concertgoers to place a glass crystal in a special pod that will trigger the lighting of the final beacon in The Mall nearby.
Bruno Peek, the pageant master of the Queen's Diamond Jubilee beacons, said the number of communities who had registered to light beacons or bonfires had surpassed all expectations.
"Our aim was to light 2,012 beacons because 2,012 have never been lit before, but by the end of the night we will have over 4,000 - that's truly amazing," he said.
But not everyone is getting caught up in the celebrations. The anti-monarchy group Republic is planning a series of demonstrations, including one at the river pageant and another two on Tuesday, at St Paul's Cathedral and along the royal carriage route.
Graham Smith, the chief executive of Republic, described the money being spent on the jubilee celebrations as "extremely wasteful" and branded the monarchy as "not fit for purpose".
He added: "We want to get rid of the monarchy and have a republican constitution with an elected head of state."
A recent opinion poll in The Guardian newspaper showed that about 22 per cent of Britons agreed with him.
The other 78 per cent, meanwhile, were gearing up for one heck of a party this weekend.