Her subjects party as the Queen goes to the Derby

Britain's bank holiday Diamond Jubilee extravaganza begin today with bunting, barbecues, house parties, and, in typical British fashion, probably some rain.

Sixty years after her accession to he throne, the racing-obsessed sovereign will begin four days of festivities by attending the Epsom Derby.

A nationwide bout of boozy partying will begin this afternoon and tonight in pubs, restaurants and homes. According to a survey by Santander, almost six million people (not all of them royalists) will hold or attend house parties over the four days.

Supermarkets have increased stocks of beer, wine and cake to cater for the £83 per head demand forecasted – £424m nationally on food, drink and decorations.

Roads are expected to be congested from 10am to 4pm today as people head to friends, relatives, holiday homes and hotels.

Tomorrow the official celebrations begin with street parties across the UK for the Big Jubilee Lunch. The first big setpiece event takes place in the capital from 2pm, when a 1,000 boat Thames flotilla – replete with the Queen and the Duke of Edinburgh in the new £1m Royal Barge – progresses from Putney to Tower Bridge; riverbanks expected to be lined by hundreds of thousands of wellwishers.

On Monday, Madness, Sir Paul McCartney, Elton John and Shirley Bassey perform on the roof of Buckingham Palace in a concert broadcast live by the BBC. An hour later, at 8.30pm, communities will light a network of 2,012 beacons across the UK, Channel Islands, Isle of Man and the Commonwealth.

The celebrations climax with a feast of pageantry in the capital on Tuesday, including a service at St Paul's Cathedral, a horse-drawn procession from Westminster Hall to Buckingham Palace, an appearance on the balcony and an RAF flypast.

A baffling multitude of events will entertain across the country – including a record attempt for the longest line of bunting, to a party in a phone box and a Jubilee-themed cheese rolling competition.

Two thousand enthusiasts will dress up in period clothing to re-enact a English civil war siege at Newstead Abbey Historic House near Nottingham.

Over the weekend villagers in Goudhurst, Kent, have created an intricate replica of the Houses of Parliament using laser-cut plywood to float on the village pond. A 21-gun salute will be held at Edinburgh Castle at noon tomorrow.

On Bank Holiday Monday a round of Double Gloucester cheese will be chased down Cooper's Hill near Gloucester, and the banks of the Humber are expected to be lined by thousands of people for the Humber Diamond Jubilee Flotilla.

TV crews have flooded into the UK from around the world, journalists eager to capture the celebrations and the view of subjects towards sovereign. Alan Watson, a member of the House of Lords, told Reuters the Jubilee was a joyous occasion for many who see the Queen as a symbol of stability: "The country has lost its empire and is no longer in the front rank of power and I really think that change has been enormously eased by her and what she represents."

Not everyone agrees: republicans from across Britain will assemble near City Hall in London tomorrow afternoon for what the group Republic described as the "biggest republican protest in living memory". Speakers include Independent columnists Joan Smith and Owen Jones, as well as Peter Tatchell.

Regardless of political leaning, the weather is unlikely to be balmy. The BBC is forecasting mostly bright and sunny conditions across many northern parts of the country during the bank Holiday weekend, but, clouds and rain in the south. Just like the Queen, some things never change.

Jubilee in numbers

4,212 number of beacons that will be lit throughout the Commonwealth

1,000 boats that will muster on the River Thames on Sunday

6,000 officers on duty to police the Diamond Jubilee celebrations

30 tonnes of Jubilee rubbish expected in Westminster on Sunday