During the next few weeks of confusion and cover-up about the Litvinenko poisoning, look out for the word ‘lead', which may yet pin the tail on the Russian donkey.

Polonium-210, the next-to-last link in the Uranium 8 radioactive decay chain, decays to lead-206, which is stable. Therefore a sample of pure polonium-210 kept for 138 days (its half life) would change into a 50-50 mixture of polonium and lead. On the other hand, a sample of polonium-210 without any lead in it would have to be fresh-from-the-reactor material.

It is very likely that the doctors treating Litvinenko tested for lead, the most common heavy metal poison. But although the news reports mentioned thallium (a byproduct in the production of Po-210), there was no mention of any traces of lead. If there was none, then Litvinenko was poisoned with freshly made polonium, only a few days old.

I suggest that any purchase of the poisonous dose through a black market route-say a dealer in Jakarta who had a contact in Kazakhstan who could get it from someone in the Ukraine, etc.-would have taken weeks between reactor and assassin. The only way to have obtained fresh material quickly would have been through the auspices of a high-level official who could smooth the way for fast transport. Now who could that have been, I wonder?