LONDON, June 8 -- The call came in at 12:15 in the morning. Paramedics from the London Ambulance Service arrived at a house on Dale Grove, a quiet residential street in Finchley, North London, and found a 19-year-old woman with gunshot wounds. They tried. The woman was pronounced dead at the scene.

By morning, the Metropolitan Police had launched a murder investigation, cordoned off the street, and issued an appeal for doorbell and dashcam footage from anyone who had been near Dale Grove around midnight. No arrests had been made. The circumstances surrounding the death remained, in the force's own language, something detectives were "working at pace" to establish.

What the Met has not said - and what the official statement pointedly lea...