The problem with writing books and not fact-checking them properly is that you get yourself tangled in knots.

At best, forced to apologise. At worst, sued.

I haven't read the one launched in Wellington yesterday. I watched the press conference and the stand-up afterwards.

There was one allegation made of note that has been denied by the current and past board chairs of the Taxpayer's Union.

But writing a book based on interviews with people, without proper fact-checking or documentation, is fraught business.

Due diligence goes a long way.

Look no further than Earl Spencer.

Princess Diana's brother who wrote a book writing off Charles as some sort of giddy widow.

Well, also in his book he claimed Piers Morgan was in-part behind the taking of photographs on Dianna attending gym in a leotard with a secret camera.

The only problem for Spencer, had he bother to check, was that Piers was not in fact the editor of the Mirror newspaper the book assumed him to be until two years rafter the photos were taken.

Piers was ropeable.

Spencer has been forced to apologise.

It should serve as fair warning that, whether it's penned in London or Wellington, you can't believe everything that's written down.