The British love eating crisps. So much so that we get through a staggering half a billion crisps a day - and that takes 17 million potatoes. So why do we love the humble fried potato snack so much, and what are the secrets behind making the perfect crisp?

In the second episode of Inside The Factory, Gregg Wallace and Cherry Healey go in search of these answers and discover plenty of surprising facts along the way.

We'll see Gregg at the largest crisp factory on earth - Walkers factory in Leicester - as he follows 27 tonnes of potatoes as they are peeled, sliced and fried to make more than five million packets of crisps every 24 hours. He'll discover how each bag is filled with nitrogen to keep the crisps from going stale - and if you ever wondered how a crisp gets it flavour then we'll get to see the inside of the factory's development kitchen, where seasoning begins its crisp life as a real food dish.

Meanwhile Cherry Healey discovers the secrets of perfect crisp potatoes, and how it is all down to a potato's sugar content. She also finds out that our noses play a central role in how things taste and ambiance can be as big factor as ingredients. Plus she follows the production of Monster Munch, where the factory transforms 96 tonnes of corn into 12 million monster feet every single day.

And historian Ruth Goodman investigates who really invented the crisp: was it the Americans, as is often cited, or the British? Ruth cooks up the earliest known recipe for crisps to uncover the truth.

Brompton's bicycle factory in West London is the largest in Britain, producing 150 of its distinctive folding bicycles every 24 hours.

In the fourth episode of Inside the Factory Gregg joins a multi-stage manual production line to make his very own bike. He'll learn how to put together 1200 individual parts. He'll also attempt to braze a bike frame together using extreme heat of a thousand degrees, a skill that takes years to master. He'll visit a leather saddle maker in Birmingham that's been making saddles for 150 years and discover how they use cowhide from UK and Ireland cows because the cold weather means they have thicker skins.

Meanwhile, Cherry Healey gets some tips from Cycling Team GB to help us all improve our pedal power. She also learns how to paint a bike frame fit for the British weather using an electro-static charge and a 180 degree hot oven. Cherry also investigates why cyclists and trucks are such a deadly combination: in London alone there have been 66 fatalities since 2011 and half of them were collisions with a truck.

And historian Ruth Goodman reveals that folding bikes date back to the 1870's, and how 70,000 folding 'parabikes' were manufactured during World War II, some of which played a role in the D-Day landings. She'll also find out how the invention of the safety bicycle in the late 1880's was used by Suffragettes to ride to rallies and spread the word in their fight for equality.