It was actually a combination of two factors, but I think the root of the problem was in ignoring what I spend a lot of my time telling clients - that you need to understand other cultures.
A couple of years ago, we decided to set up a wholly owned lobbying operation in France, and to have it run by an American. Two things went wrong.
First, we forgot about the deep-rooted hostility between France and the United States.
Gaullism is still very strong, and it partly explains the difficulties of Euro Disney. So using an American national - even though she was technically very good at the job - was an important part of the mistake. The French are very nationalistic.
I also failed to understand - although I knew this intellectually - that the French lobbying environment was different from that in the United Kingdom, the United States or Brussels.
In fact, lobbying is a kind of Anglo-Saxon art or business form. And while it is well-established there, in southern Europe (and France is part of southern Europe for these purposes), it is not such a mature form.
Lobbying is really used in France mostly as a way of getting European Union business. It is rarely used internally. This is because there is no need.
Britain has become a much more fractured society. The old Eton-type links do not work any more, so lobbying by people who understand the system has a role.
But in France there is a still a small grouping of elite institutions which the leading figures in the private and public sectors attended. They stay in touch and there are great links between the two sectors, with people frequently crossing between them in both directions.
As a result, a lot of French companies don't feel the need for outside help. And this means that lobbying work is much more limited there. It is primarily restricted to lobbying the European institutions and assisting with investment in France by non- French companies.
What I did was to over- estimate the market for helping French companies with the French government.
It was a double mistake - and all the more odd because the whole theme of what I generally say to business is: 'If you want to lobby, you have to understand countries. It is no good rolling out a programme in the same way to different countries.'
I say it with great conviction and that is what we do. It has helped us become the eighth largest public relations consultancy in Europe and the UK. And one of our perceived strengths is that we are not American.
So why did I make this mistake? At least partly, it was because the individual was so technically impressive that I thought that would outweigh the risks.
But it didn't work - and it has very dramatically underlined the power of that message. I occasionally recount the story now as an illustration of the dangers of getting it wrong.
The company we work with in France today has great connections, and that works well. In France, lobbying is still largely about knowing the right people. In Britain, it's about knowing the system. You have to remember that.