You wait ages for one royal celebration and then two turn up in quick succession. Plans for a pageant of 1,000 boats down the Thames in June next year to celebrate the 60th anniversary of the Queen's accession have been announced at London's City Hall.

The river centrepiece of the diamond jubilee celebrations will be the largest for at least 350 years – by comparison a similar procession upstream from Greenwich during the Queen's silver jubilee year of 1977 attracted 140 vessels. It will also result in a long weekend of public holidays for the second year running, after this month's royal wedding and the May Day bank holiday resulted in a four-day weekend.

The Thames procession will take place on Sunday 3 June 2012 and will inevitably be used as an opportunity to extend the summer's anticipated tourist influx before the Olympic Games, which start eight weeks later.

The Queen, who by then will be 86, will ride down the river from Putney to Tower Bridge in a Thames sailing barge temporarily converted to look like an ornate 18th-century royal galley of the sort that used to convey her Hanoverian ancestors. It was aptly described by Boris Johnson, London's mayor, as a royal quinquereme, "probably rowed by oiled and manacled MPs".

In its wake will follow craft of all shapes and sizes, from rowing boats to gondolas, tugs, steamers, dhows and wherries: everything, in Johnson's words, "with the possible exception of the Ark Royal". The fleet, more than seven miles long and taking an hour and a half to pass, will be accompanied by bands and hooters, water jets and bells from a floating belfry and from the churches sited along the river banks.

There will be fireworks and music characteristic of every decade of the Queen's reign will add to the cacophony. There will be 30,000 people afloat and a million more are expected to line the route.

"It is going," said the mayor, "to be a joyful, successful version of - err - Dunkirk. I hope. We have liquid history flowing through our city and next year we are going to make the most of it."

The organisers have written to every lord lieutenant in the country and to Commonwealth high commissioners to summon craft of all sorts. Boat owners whose vessels are seaworthy and capable of progressing downstream on the ebbing tide that day at four knots (4.6mph) will be invited to apply to take part.

Adrian Evans, whose previous experience as an events organiser encompasses the Archaos chainsaw juggling circus group and – possibly less happily – the capital's millennium celebrations, said: "We are looking for the quirky and unusual. They are all going to be decked out with union jacks and an abundance of red, white and blue ... It is going to be a monumental logistical challenge."

The Conservative peer Lord Salisbury, chairman of the Thames jubilee foundation, whose Cecil family ancestors have organised royal pageants since Tudor times, tried a touch of the demotic: "Charles II's pageant in 1662 claimed to have 10,000 boats, but I am sure that was journalistic licence. My direct ancestor at that time was Nell Gwynne, the king's Protestant whore, so that's who I am descended from."

He insisted that the funding of the event will be met by private sponsorship, but his coyness about the projected cost was ruthlessly subverted by the mayor, who is, after all, a former journalist.

"It's an £8m budget, that's the capital amount, isn't it?" said Johnson.

"It is going to be quite a lot of millions, whatever the final sum turns out to be ... it will be ... I am sure it will bring tourists here in droves," said a spluttering Salisbury before conceding that the mayor's suggestion was correct. Public funding will meet security and crowd control costs.

Mindful that he has a mayoral election before then, Johnson added: "It is quite possible that on 3 June I will be in a coracle ... but I hope to be somewhere in the flotilla." He obviously has no intention of missing the summer of fun.

• This article was amended on 6 April 2011. Owing to an editing error the original referred to vessels capable of four knots an hour. This has been corrected.