If it is deemed a hit, executives of Carlton, which is making the programme, plan more debates, on topics such as Britain's role within Europe.
Although outwardly relaxed about the programme, royal officials will be watching to see how far the streak of republicanism in society has reached in light of recent scandals. A MORI poll conducted in conjunction with the programme found 48 per cent of people believed the monarchy would not survive beyond 2050, and 35 per cent said they did not want it. Only 3 per per cent said the monarchy had any personal meaning for them.
A spokeswoman for Buckingham Palace said that, like any poll, the results of the debate would be "noted" but would not comment further. "This type of programme appears more than periodically."
The debate will feature a range of representatives from the republican camp, including Stephen Haseler, chairman of the pressure group Republic, the agony aunt Claire Rayner, the Labour MP Paul Flynn and the former Sunday Times editor Andrew Neil. Professor Haseler, from London Guildhall University, said the number of people pro-republican or anti-monarchist, while not a majority, had reached "serious" figures.
Others participating tonight at the National Exhibition Centre, Birmingham, include Terry Waite, the journalist John Pilger, the writer Andrew Morton, the MP Bernie Grant, the PR guru Max Clifford, the actresses Barbara Windsor and Samantha Janus and the nightclub owner Peter Stringfellow, who will tell viewers that abolishing the monarchy would be bad for business, by attracting fewer American tourists to London.
In another clip, Mr Neil attacks the "bizarre" notion that Britain should arrange its constitutional matters according to the dictates of tourism, pointing out that republican Paris still attracts a few visitors.
The gossip columnist and royal-watcher Nigel Dempster will tell the audience - which Carlton hopes will attract between 8 million and 10 million viewers - that the future of the monarchy rests entirely on the shoulders of a 15-year-old boy, Prince William. If he does not measure up, the institution is doomed, he says.
Lord Archer will deliver what is described as a rant against republicans, including the light-hearted suggestion that they should be beheaded.
Apart from the television audience, 3,000 members of the public, bused in from 20 cities and selected as representative, will be present in the NEC. After a break for the News At Ten, the show will resume with the results of the phone-in. Executives say the network can take up to 14,000 calls simultaneously, and up to 60,000 a minute. The question asked will be simply: "Do you want a monarchy?", with "yes" and "no" numbers to call.
One of the producers, Doug Carnegie, said they knew of the dangers of rigging the result but hoped the volume of calls would swamp any such attempts. He denied suggestions that they were trivialising the issue and said the programme was intended as a serious contribution to an important subject.
Professor Haseler welcomed the debate as "very healthy".
He said: "This is a debate about the country, the establishment and the political system, not just the monarchy. Such a programme would have been unthinkable even two or three years ago."
Growing doubts over the future of the Royal Family had been sparked by scandals involving the Princess of Wales and the Duchess of York, but now ran deeper.
"They [the scandals] were more a key that unlocked the debate; then people have begun to think more deeply about the role of a monarchy in the 21st century." He cited a growing number of younger people with republican sympathies such as the actress Emma Thompson.
Professor Haseler is a member of the Common Sense Club, which discusses republican ideas. Other members include the public-relations consultant Brian Basham and the royal biographer Anthony Holden.Reuse content