Disused phone boxes in London are being put to a novel use - as solar-powered charging stations for mobile phones.

The first of six boxes was unveiled on Tottenham Court Road this week.

The service is free to use although users will be shown adverts as they wait for their phone to charge.

Technology reporter Dougal Shaw checked one out with Harold Craston, one of the team of newly-graduated students from London School of Economics who developed the concept.