I have fished the esk between Penicuik & Lasswade since i was 10years old, and not once have i been stopped and asked for a permit.
There isn`t alot of big trout in it but there are the odd bigger fish, get a pound trout and its a belter.
In recent years I have started to fish it for grayling down towards lasswade and have been suprised to find there are grayling in this area.
Be prepared to lose flies and also fight, crawl & all manor of things to get through the undergrowth.
Very enjoyable and beautiful river.