[PW] Secret tunnel in a cellar - Book ID

[trlcr at trlib.org]

A patron of ours is looking to identify a book he bought at a library book sale in 1984.  He has provided many clues, but I have been unable to find title & author.  I'm hoping it will sound familiar to someone.
 
Description of the book in the patron's words:
 

In 1984 I read an old book, title since forgotten, about a man who entered a hidden world through a tunnel from a chamber in a cellar.  There were intelligent birds that guided boats up and down a river, "Pilot Bird" is what I believe they were called.  There was a very rough river, flowing down from a lake, where there were gold bearing gravel beds to the sea, there were seagoing pirates who preyed on the residents of the village he eventually came to. 


There was an island in the lake, with a monastery, with priests who were to eventually train him and his wife (who he met in the village by the sea).  I think the island might have been a sacred island and the priests and priestesses were for "ilona" or 'illona".

Of course, he led them to freedom from the oppressors.

 

The location of the story was in Great Britain, the tunnel was in a cellar for certain but the opening was cave on the other side, there was no magic, only "practical application" of this worlds knowledge to save the good people of the other side from the bad people of the other side....for instance, he main character, he teaches them how to make gunpowder which he learned in his military training.

 

Another point, it was an old book, I bought it in a library sale for 25 cents in 1984, and it was quite old then, probably from the first half of the century.

 

>From my memory of readin this, I'm sure that it must have been for older teens and adults, although I must add that it wasn't the greatest book ...but better than some I've seen since.

 
 
Thanks in advance,
Kristina Kauffman, Reference Librarian 
Central Reference Service 
Timberland Regional Library 
415 Tumwater Blvd SW 
Tumwater, WA 98501-5799
kkauffman at trlib.org