[This is my latest FT newspaper column, drawing on suggestions from an earlier blog post. My other newspaper columns can be read here -- most require an FT.com subscription.]

Conspiracy theorists have a bad reputation. They are usually portrayed as paranoid, isolated, deluded people, best avoided.

It is true that there are many sinister and unpleasant conspiracy theories. These are usually the ones that seek to blame all the world’s ills on a single racial or social group – Jews, Catholics, Freemasons.

But there are also conspiracy theories that are delightfully dotty. A friend in Ankara tells me many Turks are convinced that, during the cold war, the Russians infested the Sea of Marmara with a sturgeon-devouring predator that sent these valuable fish fleeing into the Russian bit of the Black Sea – thus allowing the Russians to control the world’s supply of caviar. That is a theory worthy of James Bond.

The idea that conspiracy theorists are an isolated bunch, on the fringes of society, is also wide of the mark. Some theories are so widely believed that they are now almost mainstream. A recent BBC opinion poll suggested that only 43 per cent of Britons accept the official verdict that the car crash that killed Diana, Princess of Wales, was an accident. The countless “9/11” conspiracy theories also have a surprisingly wide audience – even in America. A Zogby poll last year found that 42 per cent of Americans think the US government is “covering up” facts about the terrorist attacks of September 11 2001.

Why do conspiracy theories command such a wide audience? I have my own theory about that.

With half of Britain under water after heavy rain, it is now clear to me what Tony Blair should have said when he left Downing Street a few weeks ago: "Apres moi, le deluge."

Now – onto the main business of the day. I see that PL is worried that I am blurring the line between the column and the blog. I must admit that it is rather odd maintaining two personalities and two voices – one for the newspaper and one for the blog. But I have decided to go for a bit more line-blurring. Specifically, I wonder whether readers of the blog might help me do some research for my newspaper columns. I did hesitate before making this suggestion, since it involves dropping the pretence of omniscience which is an important part of the persona of any newspaper columnist. But I’m not sure I can even spell omniscience – let alone claim it – so what the hell. Anyway, the people who run the website tell me that what I’m proposing to do is called "crowdsourcing" (rather than laziness, as some might have it) and is extremely cutting edge. So that is some consolation.

Conspiracy theorists who would like to believe that the invasion of Iraq was all about oil will be tempted to fork out £17 for a new book – "Oil Wars" (Pluto Press). The editors carry the stamp of academic respectability – they hail from the LSE and Stanford. And they definitely flirt with the "war for oil" thesis.

The book’s introduction starts with a very suggestive quote from Paul Wolfowitz – "The most important difference between North Korea and Iraq is that economically we just had no choice in Iraq. The country swims on a sea of oil." Infuriatingly this quote is not footnoted. I would love to read it in context.

Over the weekend, I watched one of the worst films I have ever seen. "Love Actually" features Hugh Grant, cast as Britain’s prime minister. In one of the film’s most important moments, Grant insults the American president at a joint press conference. The scene has become so famous that when Douglas Alexander, a minister in the Brown government, made some ambiguous comments about the US in a recent speech, pundits eagerly debated whether Britain was having a "Love Actually" moment.

I have no interest in the thought of Hugh Grant as prime minister. But I would pay money to see Boris Johnson in 10 Downing Street – just for the pleasure of seeing him conduct a joint press conference with the US president. I am sure Johnson would be perfectly polite. But the contrast between a shambling, unkempt and inarticulate "Boris" and the slick polished style of a US president would be a wonderful practical joke to play on the Americans.