OK, thanks for the quick reply.
But...
I experienced the flashback quite a while ago,
so I don't remember where the hatch is.
Also, the link has a picture and a map to a
"tree stump" which isn't mentioned in the text of the link.
Furthernore, it appears as if this tree stump is back towards
the area you first start from, not Ledur.
Sorry if i'm being dense here!