In 1939 Polish intelligence offered to the British the German encoding machine, Enigma, plus the keys to keep decoding Wehrmacht secret messages, 80 per cent of which the Poles could read. The British, obsessed with the Empire not Europe, had focused on trying to read Japanese naval codes and showed little interest in the fact the Poles were cracking German codes before the war started.

Throughout history, intelligence agencies and secret agents are the most easily mocked of public servants. Their necessary secrecy gives rise to sinister interpretations. They have to bribe, seduce, blackmail or cajole men and women into betraying their own country or cause. They make mistakes, are venal. But they are necessary. The terror attacks are alerting a public sleepy-eyed after reading too much John le Carre to the real-time importance of intelligence. To understand what needs to be done we need to look at past successes and failures. Luckily there is now a new wave of spy books - fact rather than fiction - which examines in detail achievements and cock-ups. These new volumes are much richer than the unending sequence of spy thrillers, a genre that is running out of steam.

The endless literature on Enigma and Ultra barely mentions the contribution the Poles made in giving Churchill the priceless secret that helped win the war. One reason was the disappearance in 1945 of all the files that recorded the contribution Polish intelligence made to the Allied war efforts. As the Soviet Union rose to world power status, official London placated Sovietism by writing the Poles out of second world war history. Polish airmen and soldiers were not even allowed to march in any of the victory parades at the war's end.