British intelligence obtained information from Germany while controlling the information sent back from Britain. Control of German human sources in Britain gave deception considerable reach, alongside British human intelligence activity inside Germany. That advantage is applied to Operation Sea Lion as a counterfactual. False reports could have encouraged German landings at locations chosen by the defenders.
Notable Point · 2:25:48-2:28:59
Double Cross intelligence against Operation Sea Lion
British control of German agents offered a way to shape the intelligence behind a hypothetical invasion of Britain.