In July 2024, DHL parcels exploded in logistics centres in the UK, Poland and Germany. Each of them was powerful enough to have brought down a cargo plane had they detonated onboard.

Security services would eventually trace the plot back to a group of Russian-directed saboteurs who had a further 6kg of explosive material in their possession. That was enough to give them the capability for what security officials told the Financial Times was the next stage of the plan: to attack flights to the US, and cause more disruption to the airline industry than any act of terror since the World Trade Center attacks.

It was just one near-miss incident in a co-ordinated and covert campaign of sabotage led by Moscow, officials believe, that has sown bewilderment across the continent and is steadily posing more of a risk to human lives.