Mike - my Laurus nobilis - has come down with a case of powdery mildew; a common disease of bay trees. The treatment was severe. Mike has two parts to him, a long one and a short one. I don't know if the shorter part is a second trunk or if it's a branch of the main trunk which budded below the soil. Whatever it is, the affected leaves were all on that part, that branch, so I took the entire branch. Effectively I took a third of him. By isolating the infected part from the healthy plant I should've prevented further deterioration; fingers crossed. Mike looks sad now.
I've gotten photos, of course. The classic grey patches of powdery mildew are visible, as are the brown leaf margins which suggest the mildew has damaged the leaves internally.