National celebrations to mark the Queen's diamond jubilee have begun as the country geared up for a weekend of pomp, pageantry and fun in honour of its monarch.

Events staged in tribute to the Queen's 60-year reign will be held across the UK during the extended four-day Bank Holiday, with spectacular public activities planned for the capital.

The Royal Navy warship HMS Diamond signalled the start of the festivities in dramatic fashion by firing a 21-gun salute that boomed across Portsmouth Harbour on Friday.

Tributes have been paid to the Queen from two national figures - Prime Minister David Cameron and the Archbishop of Canterbury Dr Rowan Williams - with both agreeing on the importance of the country's head of state.

And a poll suggests a large majority of the UK public, 80 per cent of those questioned for an Ipsos Mori diamond jubilee survey, want to remain a monarchy.

Mr Cameron, interviewed by Sky News, was asked whether he thought the Queen might step down one day in favour of her son the Prince of Wales.

He replied: I wouldn't anticipate that. What I see in Her Majesty is someone, in spite of the fact she's been on the throne for 60 years, in spite of the fact that Her Majesty and Prince Philip are now relatively elderly, there is an extraordinary level of physical energy, mental energy, and above all devotion to her people, to the institutions of this country, to the way our democracy works."

The prime minister will join senior royals and prominent individuals from the UK and abroad, including New Zealand Prime Minister John Key, at many of the events.

Details have emerged about a special musical tribute to the Queen on Monday night, in which pop veterans Madness will perform their hit, Our House, on Buckingham Palace's roof during the diamond jubilee concert.

Other stars appearing include Stevie Wonder, Sir Paul McCartney and Sir Elton John.

Preparations for Sunday's diamond jubilee river pageant are in place, with up to a million people expected to line the banks of the River Thames and nearby open spaces to watch the 1000-strong flotilla sail through London.