Very highly recommended road if you're ever in this part of the world. Either way - Steeple Bumpstead to Finchingfield road.
I did it today on my way back to London. Luckily there wasn't another soul on it and I swear I was smiling for every inch of it
Know this route well and can second that it's a quality bit of road, as are the surrounding roads. Word of caution though, this area is a bikers playground and has been for years. It can be and often is, heavily policed.
