text: 2 October 2015 Last updated at 18:13 BST
  Speaking in an interview with BBC Newsnight's diplomatic and defence editor Mark Urban, he said UK policy in Syria had been hampered by "wishful thinking" - and officials underestimated the staying power of President Bashar al-Assad.
  More on this story from Mark Urban on BBC Newsnight at 22:30 BST BBC Two on Friday 2 October, and afterwards on iPlayer
target: Russian's intervention in Syria is "hugely significant" says the UK's former senior military adviser in the Middle East Lt Gen Sir Simon Mayall.