Bill Gates explains which 'superpower' he'd choose to help poor

If you could choose one superpower, what would it be?

That's the question school children in the US put to Microsoft founder Bill Gates, and his wife Melinda, and their answers - more time, and more energy - led to a new outlook on how to help the world's poor.

The couple outlined their strategy in the Bill & Melinda Gates Foundation's Annual Letter, an open note written to high school students that proposes new ideas in their charitable work.

They spoke to the BBC's Laura Trevelyan about how these super-human abilities could bring about real-life change in developing areas.

Produced by Mat Morrison, filmed by Mark Hiney, edited by Bill McKenna