There are two: the first was the launch of Guardian Unlimited in 1999, which has expanded the reach of The Guardian exponentially, getting the brand into the minds of people who would never have been exposed to it. Business plans mean very little when you're working in a dynamic medium like the internet. You can have the most brilliant strategy, but if it doesn't work, you have to change it as you go along.
My best decision, though, has to be relaunching The Guardian as a Berliner.
Why? People are going to look at it now and say this was a no-brainer.
It was the editor's vision, which I backed commercially, but it was an unpopular decision at the time because no-one knew what a Berliner was.
It meant an 18-month wait for new presses, and a complete change in the way we distribute the paper and trade with the advertising community.
But it keeps the broadsheet sensibility, and page-dominant advertising in it has more impact than the equivalent sizes in broadsheet. It was a bold decision commercially and editorially.
Having made the best decision of my working life to date (the Berliner format), the scale and ambition of the project barely hit home. We had one full-time job trying to keep the current paper on track and make sure sales weren't terrible, but quite a lot of us were doing another full-time job running this huge project. In addition, we made the decision to move lock, stock and barrel out of this building in Clerkenwell to Kings Cross in 2008.
It was the right decision, but it put a lot of people under pressure. Looking back on it now, to say that we've got through it and we haven't screwed up - that's great, and we're further ahead than we would have been. But if I had my time again I'd probably have cut us a bit of slack. When you have such an ambitious project, you should think about what else you take on at the same time.
For me, it was pretty bloody hard work but, as with most bad decisions, you learn from them and if you get through them, you are the stronger for it.