Business intelligence firms who compile reports on corporate subjects find their targets are fighting back

In John le Carré’s landmark espionage novel Tinker Tailor Soldier Spy, undersecretary Oliver Lacon ­outlines the obvious ­problem in unearthing a traitor at the heart of the British secret service. “It’s the oldest question of all, George,” he muses to the hero, George Smiley. “Who can spy on the spies? Who can smell out the fox without running with him?”

Yet in the modern setting of ­corporate intelligence – an industry that collates research on the business world and employs its fair share of former state-agency operatives – there appears to be no such issue.