The man in the white suit and his friend in the dark, double-breasted suit walked up to the cream gate and pressed the grey metal bell twice, but there was no-one in. The only person who responded was a policeman who sauntered up the road to see what was going on.
The house, a magnificent property dating from the Restoration period, is the country home of Tony and Cherie Blair, who live in the only constituency in Great Britain where absolutely no one will be voting Labour on 6 May.
Martin Bell, that veteran campaigner for cleaning up parliament and breaking the hold of party whips, was in the vicinity trying to drum up support for an independent candidate, John Stevens. They were hoping to see the constituency's most famous couple to canvass their support, but the only sound from across the high wall was the drone of a motor mower. The Blairs have invested a lot of money in their magnificent garden, which leads down to an ornamental lake. The view is fabulous.
It's the Blairs' bad luck that the village where they have made their home is just inside the parliamentary seat of Buckingham, which has been held since 1997 by John Bercow, elected Speaker of the House of Commons after his predecessor, Michael Martin became a casualty of the expenses scandal.
There is a decades-old convention that none of the main parties puts up a candidate in the Speaker's seat, because his job requires him to be above politics. It's a convention agreed by politicians without reference to the voters, and may not last many more years, judging by the resentment it has aroused in Buckingham.
The irony is that if John Bercow had run again as a Conservative, as he has in three previous elections, he would sail home. In 2005, he collected more than 60 per cent of the vote. As it is, he will be the first speaker ever to have a real fight on his hands at election time.
A flock of candidates has moved into Buckingham to fill the vacuum left by the Labour and Liberal Democrat parties. At least eight have got their names onto the ballot paper. There could be more by the time nominations close next week. Most will be lucky if their vote hits more than double figures, but two have makeshift organisations behind them and are knocking holes in Mr Bercow's vote. They are Nigel Farage, of the UK Independence Party, whose politics are well to the right of Mr Bercow's, and Mr Stevens, to his left.
Mr Stevens is a former Conservative MEP for the Thames Valley region, who was deselected prior to the 1999 European elections, because he was far too enthusiastic about the EU for his party's taste. He set up a new political organisation for pro-EU Tories, which didn't last long then joined the Liberal Democrats, but parted company with them a year ago.
His cause has been taken up by Martin Bell, a former BBC journalist who made his political debut standing on an anti-corruption ticket in Tatton, which was one of the safest Tory seats in the country until Bell took it from them.
Since he stood down in 2001, Mr Bell has been trying to encourage independent candidates to come forward to break the hold of the party system. He thinks that, if the speaker were defeated, it would send a salutary shock through the whole system.
"The speaker has more unfettered power than almost anyone else in the country, apart from the prime minister, so it's very important that the speaker is universally respected and admired," he said. "I thought John Bercow deserved a fair wind in the early months but now I feel that his personal conduct has been wanting."
John Stevens, sitting alongside Mr Bell at a sparsely attended public meeting in Buckingham Town Hall, was less restrained in attacking his opponent, both over his political record and his expenses. Mr Bercow "flipped" his second home between London and Buckingham to avoid capital gains tax. He has been told he must pay back £6,508. In the 1980s he was an ardent Thatcherite but he has mellowed in middle age, and his wife Sally is a Labour party activist.
"He has become speaker through an extraordinary political parambulation from the extreme right to the soft Blairite left," Mr Stevens said. "It was the most partisan election of a speaker in living memory.
"The speaker is symbolic of the whole parliamentary system. There is an absoutely imperative need to draw a line under the expenses scandal. Defeating the Speaker, which has never happened before, would send a dramatic and cathartic message."
Mr Bercow's other main opponent, Nigel Farage, was leader of UKIP until he resigned to concentrate on contesting Buckingham. He had a highly publicised campaign launch this week, and will collect votes from locals who think that Gordon Brown and David Cameron are soft on immigration.
Random conversations with voters in Buckingham suggest that a huge proportion of them know they will not be able to vote for any of the main parties because their local MP is the speaker. This is not a popular development. Whatever they think of politicians, they don't like being denied the right to vote as they choose, and it may be that the long-term answer is – as Mr Stevens suggests – to switch to the Australian system, under which the speaker ceases to be a constituency MP.
As it is, Mr Bercow is campaigning with a green and gold rosette, representing the colours of the House of Commons, and explaining to everyone he can reach that it was not his idea to give the speaker a clear run, and to warn against voting for fringe candidates. He reserves the most caustic remarks for Nigel Farage.
"Mr Farage can shout and scream all he likes, but he would have no allies whatsoever if he ever got into Parliament, and so he would have no influence," Mr Bercow told one voter as he was canvassing yesterday in the village of Edlesborough.
Speaking to another, he said: "Electing a fringe candidate would be a very retrograde step for the constituency. People are entitled to their views, but I don't think the constituency wants to be represented by a singe-issue fanatic. I don't want the constituency I love to become a laughing stock."
His other pitch is to point to his 13-year record as a constituency MP, taking up "thousands" of cases. Going from door to door, he came upon a succession of people who didn't like being denied the choice of voting for a political party, but promised to vote for him anyway because of his local record.
The mood changed suddenly, though, when Mr Bercow approached George Zaleski, a 51-year-old computer engineer, who waved his arms and shouted at him to "get off my property". Mr Zaleski has been off work suffering bouts of concussion from a road accident three years ago, and felt that Mr Bercow should have supported him when he lodged a complaint against the NHS. He will vote for Mr Stevens. "Politicians should be selfless. They should be there to help people," Mr Zaleski said.
Alan Grigg, a former parish councillor, passing by with a copy of the Daily Telegraph under his arm, avoided talking to Mr Bercow though he possibly may vote for him. "There are a lot of people inclined to vote for UKIP, and I don't think everybody in Buckingham is a fan of John Bercow – but UKIP haven't a hope in hell of actually getting in," he said. "I would have voted UKIP a few years ago but it's too late now. We're too embedded in the EU."
Mr Bercow has not canvassed Tony or Cherie Blair, but hopes and expects that they will vote for him. However, Mr and Mrs Blair will find a leaflet in their letter box, left yesterday by Mr Stevens, suggesting that they might like to lend their support to an independent. But given that Mr Stevens wants to overturn the political system, on which Tony Blair's career was built, we can assume that that is unlikely.
Buckingham: Result in 2005
Conservative Bercow, 27,748, 57.4 per cent
Labour Greene, 9,619, 19.9 per cent
Lib-Dem Croydon, 9,508, 19.7 per cent
UKIP Williams, 1,432, 3 per cent