David played  rhythm guitar and actually founded Dire Straits.
His brother Mark came into the group. David played on the
1st two CD's put out by Dire Straits and then dropped out.
In 1983 he put out an Album called "Release" which became
a favorite of mine. I had an old Album version of it and was combing the internet a few years ago and came across his site:

http://www.knopfler.com

Turned out he held the rights to that album and 6 others that
he had released since then. He privately produced these albums
with the identical liner notes except on CD. If you hear these Albums you will immediately notice a distinct voice similarity.
If you like Dire Straits you would like the album "Release".
David can be reached at [email protected]

--Pat