Security reviewed across UK after Berlin Christmas market attack

One of London's most popular tourist attractions will be protected by strict road closures as police in the UK react to the attack in Berlin. Twelve people died after a lorry ploughed into a crowded Christmas market in the German capital on Monday night in what is assumed to be a terror attack. It came just hours after Russia's ambassador to Turkey Andrey Karlov was shot dead at a photography exhibition in Ankara.