The distinguished broadcaster and naturalist, Sir David Attenborough, has been on a visit to the White House at the personal invitation of US President Obama.

The president, who is said to be a great admirer of Sir David's work, wanted to discuss the future of the natural world.

David Sillito reports.

Watch 'President Obama in conversation with Sir David Attenborough', on BBC1 at 2230 on Sunday 28 June