Tehran's streets at the height of the morning rush hour resemble a vast, sprawling car park. Bumper-to-bumper traffic, much of it stationary, the acrid steam of a thousand exhausts hanging in the cold winter air. If you wanted to kill someone, this would be the moment to do it: when they are stuck in their cars – sitting targets.
At 7.40am last Monday, in north Tehran's Aghdasieh district, a motorcycle threaded its way through the long lines of cars on Artesh Boulevard. It edged up to a silver Peugeot 405, hesitating alongside for moment, before moving off into the maze of vehicles. A few seconds later there was a bang from the side of the Peugeot, as a small bomb stuck on to the window detonated, killing one of the men inside. The driver and a woman passenger were wounded.
It is certainly true that, while the discovery of any involvement in the killings of civilian scientists would be career-endingly embarrassing for the CIA or MI6, the Mossad is known for such exploits. It is widely believed to have killed scientists working on Iraq's nuclear programme in the 1980s.
The outgoing Mossad director, Meir Dagan, has stepped up the use of assassinations against Israel's enemies, and has won plaudits for doing so. The Israel Hayom news website remarked on the occasion of Dagan's retirement: "[He] will be leaving an organisation that is far sharper and more operational than the organisation he received, and all of the accusations from Tehran yesterday are a good indication of that. Iran will be the focal point for the next Mossad director, too."
One of the US cables made public by WikiLeaks describes a meeting of a US-Israeli joint political military group in November last year. It said: "The GOI [Government of Israel] described 2010 as a critical year – if the Iranians continue to protect and harden their nuclear sites, it will be more difficult to target and damage them. Both sides then discussed the upcoming delivery of bunker-busting bombs to Israel, noting that the transfer should be handled quietly to avoid any allegations that the US is helping Israel prepare for a strike against Iran."
The bombs duly arrived a few months later. The WikiLeaks cables also underpin a prediction made by western military officials earlier this year, that if Israel flew above Saudi Arabia to reach Iranian targets Saudi radar operators would somehow "fail to see them".
n September last year, Barack Obama announced the discovery of a secret enrichment plant burrowed into a mountain near the city of Qom.
But the US, Israel and other western spy agencies have also spent years slipping faulty parts into black market consignments of equipment heading to Iran – each designed to wreak havoc inside the delicate machinery requirement for enrichment. Iran has now accumulated 3,000kg of low-enriched uranium – enough for two weapons, if further enriched. And this year Iranian scientists have stepped up the level of enrichment they are working on to 20%, which in terms of the technical obstacles that need to be overcome, is well on the way to 90% weapons-grade purity.