John Martyn was a Scottish singer-songwriter-guitarist who came up about the same time, and with the same Joe Boyd management, as Fairport Convention, the Incredible String Band, and Nick Drake, with whom he formed an odd-couple friendship. John passed away a few years back. Early albums with Danny Thompson on bass are classics, more 'produced' later work is (IMHO) sometimes a mixed bag but I too love 'Grace and Danger'. My idea of a good intro/overview would be 'No Little Boy', kind of a greatest hits re-recorded with all-star friends like Phil Collins, Levon Helm, Peter Erskine, David Gilmore... Here's a YouTube playlist of NLB (with a couple non-Martyn songs for some reason). I'd buy an atmos remix in a heartbeat. He's a vibe.
John Martyn-No Little Boy