Stray rubber hose on a Mk2

Next to the radiator expansion tank there is what looks like a purge filter. At the bottom a rubber hose is attached. The other end is just hanging loose. It has a plastic plug on it which looks to be broken. I think this is no more than a breather pipe but I cannot see where this is supposed to go. Anyone have the answer please?

It would push into a hole in the front subframe, it’s the breather for the charcoal canister.

Thanks Robbie