Finnish mobile phone maker Nokia has launched two new smartphones based on Microsoft's new Windows Phone 7.5 operating system.

The Lumia 800 and the Lumia 710 mark the beginning of Nokia's fightback against Apple's iPhone and rivals using Google's Android software.

Rory Cellan-Jones took a look at the Lumia 800 model at the launch event in London, discussing it with Ben Wood of CCS Insight.