Finally removed the 17mm acorn nut from the end of the rear fuel pump by using vice grips to stop the banjo fitting from rotating. However, I'd recommend placing rubber hose over the vice grips so that you don't scratch/gouge the banjo fitting. The 17mm acorn nut came right off with no effort, however I damaged the check valve nut by using a cheap chinese made 17mm open end wrench. Never again.