In game theory – which by the way was used with extraordinary effect to extract the maximum amount of money from phone companies when licences were being auctioned back in 2000, very nearly breaking them in the process – there is a concept known as “the prisoners’ dilemma”. This posits that two otherwise “rational” individuals might choose not to cooperate, even if it appears that it is in their best interests to do so and it damages them not to. Building mobile phone masts provides an interesting variant on the principle. If mobile phone operator A thinks his mast is going to get used much of the time by the roaming customers of mobile phone operator B, he might well decide not to build it in the first place. Conversely, A has even more incentive not to build it if he thinks that his customers can merely piggy back off B’s infrastructure. The result is that nobody builds the mast to solve the “notspot” problem.