Dr Richard Fitton:
I think it is the same with any technology. The greater the penetration geographically across different types of people and property and heating systems, and the greater the spread the better. It is a very difficult question to answer. My thought has always been, when is the roll-out complete; when do we say it is complete? Is it at 90%, or 80%? It may be that 10% of people—I have just made that figure up—will not let you through the door. When is it complete; when do we rubber stamp it?