How to catch a jackal

The remake of Frederick Forysth’s ‘Day of the Jackal’, currently streaming on Peacock and Sky, starts with a very long shot. The Jackal makes the shot from a 30-story tower block in Munich, through a revolving door, and into the back of a politician’s head 4,210 yards away. The bullet takes six seconds to arrive. The target’s security detail turns around, scans the skyline, and settles on a 17th floor window with fluttering curtains. More than 2 miles away. It’s an expedient device for keeping the pressure on shooter Eddie Redmayne to skedaddle, but come on. What they really needed was ‘sound ranging’, a method first developed by a band of First World War physicists.

In spring 1917, the Canadians Corps was bedded down on the western edge of Vimy Ridge, halfway between Dunkirk and Paris, trading fire with the Germans, who had held the Ridge since early in the war. It was a hellishly difficult position to take; 200,000 Frenchmen had died in three attempts. Enemy guns fanned out on the eastern edges of the Ridge, stretching back miles.

Minutes before 5:30am on April 9, the Canadian guns went quiet. “There had been an ordinary amount of night firing, our batteries and machine-gun fire. But about five minutes before Zero Hour, there had been an eerie, almost complete silence”.

Andrew McNaughton, a young Counter Battery Staff Officer, an engineer by training, had traveled with the newly incorporated 7th Canadian (McGill) Siege Battery, students and staff from McGill University, drawn by the recruitment office’s slogan “Calling on men of trained intelligence.” McNaughton had sought out the help of William Bragg and his team. Bragg, who was and is the youngest technical Nobel laureate, brought his sound-ranging team and a technique that compared when the sound of a gun's boom arrived at microphones spread far apart to pinpoint the source.

Within three to five minutes, they could give an artillery team the precise coordinates of the shooter.

At Zero Hour, in driving sleet, the Canadian Corps started their assault. “On the stroke of 0530 hours, a bombardment of terrifying intensity burst on the enemy forward position … From the German lines multi-coloured rockets soared in mute appeals for aid”. The Canadian artillery pounded the German front lines, pushed beyond to their support lines, and then further back to the Black Line, the main German defenses. “I felt that if I had put my finger up, I should have touched a ceiling of sound.” The big German guns barked back and the sound rangers were in business.

Every reply from the German guns was a giveaway, another clue that the sound rangers could decode and pass to the Canadian siege batteries for targeting. The biggest of the German guns was dug in 11 miles beyond the Ridge. Sound-ranging works best when listening across a wide angle, so three teams fanned out behind the Ridge and compared readings. As troops advanced on the Ridge, every yard hard won, Canadian gunners picked off the enemy’s heavy artillery. Over three days and nights, 84 big German guns, 80% of their capability, gave themselves away and were silenced. Eleven miles to the east, the Germans’ largest artillery position was flattened. By nightfall on April 12, the Canadians held the Ridge. Canadian servicemen, recovering in London, were “inclined to attribute the crushing character of the Bavarian collapse mainly to artillery work”. The sound rangers had guided their hand.?

There are millions of microphones out there now. It would take only a few and a bit of trigonometry to figure out where the Jackal's shot came from.

Mind you, he was out of there in under three minutes so probably still would have gotten away with it.