Mohsen Fakhrizadeh was a marked man

There are three stages to making a nuclear bomb. First, the fissile material must be produced, which in Iran’s case is uranium. Then comes weaponisation, which means shaping the material into a warhead. Finally, you need to attach it to the means of delivery, usually a missile.

From an Israeli point of view, denying Iran the bomb means dealing with all three of these stages. Some people say that the fire at the uranium enrichment site in Natanz, Iran’s largest such facility, in August, was caused by the Mossad. That would be disrupting the fissile material stage.

In terms of the third stage, Major-General Qasem Soleimani, the Iranian military chief who was killed by an American missile, was involved with funding the nuclear programme and the means of delivery. His departure was a big hole in organising the means of delivery of the bomb.

Fakhrizadeh’s specialism was in stage two, weaponisation. There is only a small number of experts in Iran who understand the weaponisation process — we’re talking double digits. He was the foremost of them. His departure has created a vital break in the chain towards a viable nuclear weapon.