Found Plastic behind timber cladding

[AlBob]

We had external wooden cladding removed from between ground and first floor in our uk 60s build and this is what was revealed. It's now been clad back over in hardie plank but I wanted to know if people knew what the plastic was protecting and what would have been directly behind it e.g. ends of the floor boards (or would they sit above), a beam or something else?

Thanks for your help

 

[^woody^]

Photo is too blurred

 

[AlBob]

Sorry I don't have a better shot but for context: the house is to the right of the picture (taken from scaffolding) where you can see the ground floor windows and above that two beams with some clear plastic in between. My question relates to that plastic.