How a crippling shortage of analysts let the London Bridge attackers through

Last Tuesday, in the wake of the latest terror atrocity to strike Britain, the former head of MI5 Dame Stella Rimington recalled just how primitive intelligence gathering used to be. Addressing a conference of security officials in west London – four miles from London Bridge where the terror attack had taken place three days earlier – Rimington recounted an anecdote about how her spy training in the 1970s involved infiltrating a local pub to eavesdrop on targets.

Over the four decades since then, intelligence gathering within Britain’s security services has evolved beyond comparison. Eking out a lead is no longer an issue – instead extraordinary volumes of information are relentlessly harvested electronically. The worry, according to experts, is whether they are acquiring too much.