There is a bittersweet story towards the end of Christopher Andrew’s magisterial centenary history of the security service that has all the ingredients one might expect from this spy-catching narrative. In 2001 a disgruntled British Aerospace security guard tried to sell secrets to the Russians. He sent a document to the Russian embassy with a Post-it note attached, telling the embassy staff that if they were interested he could supply more documents and encouraging them to contact him on his pager. Soon a Russian intelligence officer contacted him. ‘Volodya’ met the guard at a hotel in central London. Volodya was, of course, an MI5 agent. A concealed microphone failed to work and the security service photographer had his view obscured by a hotel piano, but the guard did enough to ensure his arrest and subsequent conviction. When the details were known, the Russians objected to MI5 impersonating a Russian security agent.

It’s not quite Bond or Le Carré, but it is a fair representation of what the security service has spent a great deal of its century doing. It is striking that for much of that time spies were pretty easy to catch, except for Soviet spies. Indeed spies