In pictures: how your favorite fast food chain became a household name

Think fast food and it’s likely a few world-beating burger brands spring to mind. Whether it's drive-in, drive-thru or eat-in, they are today ubiquitous across the globe. But their hearts are in the USA, where McDonald’s, In-N-Out Burger and KFC took the brakes off cooking in the 1940s and 1950s, and changed the way we eat forever. Here’s how it happened...