With millions of people enduring pay freezes and cuts, the national minimum wage is supposed at least to guarantee that pay cannot drop below a legal minimum level. But as the adult rate rises to £6.08 an hour, Panorama goes undercover to reveal how some employers exploit loopholes or get round the rules so workers do not even get paid that minimum. And it speaks to others, especially the young, who feel they are being forced to accept low - or even no - pay just to get work.