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Afghanistan security examined by Sir William Patey

30 August 2012 Last updated at 13:31 BST

Former British ambassador Sir William Patey, who left Kabul in April, says he is "cautiously optimistic" about the future of Afghanistan.

In the latest of a daily series of essays for The World at One, he said Afghanistan was not "set to become a model liberal democracy" and would remain a "fragile unstable state with weak institutions and higher levels of corruption than is healthy for any country".

Sir William spoke after five Australian soldiers were killed in one of the bloodiest weeks for forces in the country. UK and US troops aim to withdraw by 2014, and next week, the British Defence Select Committee will be asking how the future of Afghanistan can be secured.