Two metres into passage.
The void in the roof past the last lintel leads up to a modern hatch, presumably
this originally communicated with a dwelling structure above.
We were astonished to find a cigarette packet (ringed) at the end of the
passage. The idea that someone goes to the effort to journey to a remote island,
find an obscure prehistoric monument, crawl for two metres into a tiny space, and then considers it OK
to drop litter inside just mystifies us.