down in the dark 

That looks fun and your my first video fav !!! :D

i just regret the radius of my torch wasn't a little bit larger

and: did you find your coffin ??? ;-)

This is down in this building, of which the purpose i still don't know:

:-)
now we get the whole story puzzle by puzzle ... - that's very nice!

There are several buildings like this hidden mostly by undergrowth in several places in the UK. I believe (but not an expert) they are a sort of pill-box from WW2. Usually found along rivers & railways ;)

Some are padlocked so possibly have more to reveal, there again thinking about it a padlock is not such a problem :D

Ah, i think you solved it... and indeed, it's along the river! Must be a pillbox then! I heard of bunkers, but not of these.

If you google images for pillbox, you'll find many different designs and types :)