Simon Parkes takes a look behind the scenes of Britain's favourite snack, the biscuit and as he discovers major change is underway to some of our most famous food brands.Our most popular biscuits, including the digestive and the Bourbon became firm fixtures of British life in the 19th century. The snacks were produced in their millions in places like Reading and York and exported all over the world. Today, we spend more than 2.5 billion pounds eating our way through an ever increasing range of biscuits.It's a world that's now having to adapt to a number of powerful trends. Firstly, as we're being encouraged to eat more healthy foods, millions of pounds are being invested by manufacturers with the aim of "reformulating" some of the most valuable recipes in the food industry. Secondly, with the rise of global food brands, more and more of these iconic snacks are being bought up by a small number of companies.What does all this mean for a British food institution? Simon Parkes takes a close look at the pleasures and the profits behind the biscuit.Producer: Dan Saladino.