What caused Bo Xilai's downfall?

Neil Heywood, the British businessman found dead in a hotel room in China, was not working for British intelligence according to the British Foreign Secretary William Hague.

Mr Heywood had established close links with Bo Xilai, a senior Chinese politician, who's now accused of tapping the phones of Communist party leaders.

The BBC's Mukul Devichand has just returned from Chongqing where he found a city under the iron-grip of Bo Xilai, a grip that has threatened Beijing's rule in a way not seen since Tianammen Square.