This is my husband’s theory:

Detectives investigating the death of Alexander Litvinenko were last night examining the possibility that the former spy killed himself to discredit Vladimir Putin.

Increasing concerns over the reliability of the Russian dissident’s death-bed testimony have prompted police to check every detail of Mr Litvinenko’s version of events on 1 November, the day he said he was poisoned.

[…]

Some reports in the Russian press have suggested that Mr Litvinenko’s death could have been a “martyrdom operation”, on the grounds that no state would want to attract the attention of a radioactive poison plot.

But British officials warned against assuming that the spy staged his own dramatic demise.

One senior source warned: “You have to remember this guy was on his guard 24 hours a day. Normal assassination methods may well not have worked.”

You would have to be pretty committed to your cause to do something like this. To me it seems pretty extreme but who knows? People have killed themselves over less.
(via)