An uncompromising violent extremist movement, the Islamic State in Iraq and Syria has an unlikely, secular, ace in its pack - or rather a king.

More precisely, the King of Clubs, as Izzat Ibrahim al Douri - the most senior surviving member of Saddam Hussein's inner circle - was dubbed in the US Most Wanted deck of cards issued during the hunt for members of the Baath Party.

The former deputy to the executed dictator, al Douri has been reported to have died, twice.

But he has emerged as a galvanising figure behind the enormous success that ISIS has had during its offensive in northern Iraq.

He evaded capture by the Americans and formed the Naqshbandia group of Baathist officers, all of them hardened by war with Iran in the 1980s, to lead attacks against US and allied forces during their occupation of Iraq.