The beloved meal deal is somewhat of a national treasure here in the UK, with so many of us relying on them most days for a quick and delicious lunch.

But many of us never really give the thought of how our BLT or cheese and ham sandwich is made.

Now, a video showing how pre-packaged sandwiches are made in bulk has been shared online, and some sandwich eaters are saying they've been 'put off for life' by the behind the scenes process of getting sarnies made and ready for us to eat.

A video from creators How It's Made, which was shared on YouTube by the Science Channel last year, has now wracked up hundreds of views and horrified many with the shocking reality of how these sandwiches are created in a factory using specific processes.

Science Channel

One part of the video shows how sandwiches made with specific requirements and ingredients can use machines alongside manual labour to create the sarnies we see on supermarket shelves.

The camera pans across workers loading fresh sliced bread into an automated machine, checking for flaws and removing any bread slices that look less than perfect.

A machine then separates the bread before a roller spreads out the butter onto each and moves the slices to the next stage for mayonnaise to be spread.

Workers step back in for adding fillings, especially when 'more specific' ones have been requested.

The documentary shows worker's hands adding grated cheese and cold cuts of ham to each sandwich and putting them together before a machine then slices them neatly into triangles to be packaged.

Science Channel

In another part it shows the bulk process for creating sandwiches with the same ingredients as part of a fully automated assembly line covering everything from mayonnaise spread to mixing the filling and assembling the sandwich.

The documentary pans across an assembly line putting sandwich filling onto bread using a nozzle before a machine's robotic arm then slices the sandwiches and puts them together for packaging.

While some horrified viewers have been left swearing off sandwiches after witnessing some of the pretty gnarly-looking fillings, some have been left mildly impressed.

One YouTube viewer commented: "My biggest take away is that the two halves in the pack arent from the same sandwich."

As another wrote: "That's really interesting, I've always wondered how premade sandwiches/wraps are made!"

Science Channel

One aspect of the documentary that many viewers picked up on were watching some of the workers touching and picking up sandwiches with their bare hands, as one viewer pointed out: "It’s great how the workers use their bare hands to feel the connection of everyone before and after them who has touched the sandwich."

Another agreed as they wrote: "as someone who works in a school kitchen, it's blowing my mind to see these workers handling food that will go out to millions without any form of glove".

And another sarcastically added: "I like how the workers are wearing hair nets and aprons and all sorts of food safety gear to prevent contaminants from getting into the sandwiches but then they handle them all with their bare hands.

"We all know the hands never get dirty and don't need protection gear to avoid contaminants getting into the food."