He should know, of course: Vodafone has been involved, and is still involved, in tax cases involving mind-boggling sums. The £2bn case over the Luxembourg subsidiary used during the Mannesman merger deal is the most interesting, to my mind. (Read the court documents here).

But what's more interesting is the rise and rise of the tax director. The group head of tax at a multi-national is no longer the tax geek who knows how to fill in tax returns or understands the whizzy tax schemes. They have become the point man in the increasingly important debate about tax and corporate social responsibility.

I'm sure I'm not alone in finding Walters' views on tax avoidance fascinating, and intrinsically quite plausible too, on some levels, though I also feel I don't entirely have the information to judge how 'rare' tax avoidance is among multi-nationals. Perhaps it feels rare to tax directors, and rife to the layman?

My point is that Walters is not the only person putting their head above the parapet. Not only are tax directors all on the important committee hammering out the new foreign profits rules, catching everyone's attention at present, but we are finding they are also increasingly prepared to meet with us and talk to journalists generally. I know who more of them are and could tell you the names of a dozen or so tax directors at UK-based multi-nationals, something I couldn't have done a year ago.

If the interest in tax avoidance, as the Guardian/Tesco affair suggests, continues to grow in interest and importance, the tax directors will need to be more visible to explain what is going on in a complex area that is also of key public concern.