A city is on fire. The UK fights back. Russia and Britain both have nuclear weapons. Will either country use them?  -Russia knows our weaknesses. But do you? A major five-part series from Sky News and Tortoise which imagines how a Russian attack on the UK could play out – and invites real-life former ministers, military chiefs and other experts to figure out how to defend the country. Written and presented by Sky News' security and defence editor, Deborah Haynes.