Vladimir Putin appears to be relishing his role at the centre of the diplomatic manoeuvring over Syria - it reinforces his image as the strong man in the Kremlin. But just how strong is he? A recent round of Russian municipal elections gave the anti-Putin movement a much needed morale boost. HARDtalk speaks to the opposition activist and former world chess champion, Garry Kasparov. Is there any serious challenge to the supremacy of Putinism?