You're tucking hungrily into a glorious bag of your favourite brand and flavour of crisps and there it is, a nasty and unwelcome surprise: a crisp that is not golden in colour but a weird off-looking green.

Are you brave enough to eat it? Or do you discard it like the scoundrel of a crisp that it is?

Either way you may find yourself pondering whether or not eating it will do you any harm.

Just why is it so green? Can they do me any harm if I ingest it? Will it taste as disgusting as I suspect it does?

Green potato crisps have now become the subject of Channel 4 show, Food Unwrapped , and there are answers to all the above.

What causes some crisps to turn green?

You'll be relieved to hear that it's not something unduly worrying or dangerous.

Co-presenter Matt Tebbutt visited a Norfolk farm to get an explanation - and it's pretty simple.

Potatoes grow underground and are therefore shielded from sunlight. However, if parts of them start to grow above the ground, they then are exposed to light and will start to change colour.

That's what accounts for the green hue - it's simply chlorophyll, a pigment which is intensified by light.

Are the green crisps safe to eat?

Well, not entirely.

Chlorophyll can contain a chemical for solanine, which is the same toxin produced by deadly nightshade.

However, those playground fears about the a green crisp's noxious qualities may not be fully justified.

Matt talks to a farmer who points out if you eat a lot of green crisps, then no, you won't feel very well.

To put this into perspective, Matt then adds that despite the toxin being poisonous you would have to eat one large entirely green potato to become unwell.

To be fair, we're probably still going to continue binning every green crisp we encounter.