Behind closed doors in the Downing Street Nudge Unit

At the heart of Downing Street, a select group of strategists known as the Nudge Unit aims to alter our behaviour.

This could be encouraging people to stop smoking perhaps, or to eat more healthily - without bringing in new laws or regulations.

When Radio 4's PM programme's Becky Milligan was invited to sit in on one of its brainstorming sessions, she heard how subtle differences in approach can achieve the desired result.

PM is broadcast Monday-Saturday at 17:00 BST on BBC Radio 4 and is also available on the BBC iPlayer.