Ah the infamous A339. The site of several deaths lately. It's a great, technical road with a good surface, but beware. High speed corners + miscalculation = risk of severe trauma/death. If you want to do it, ride the road several times up and down below the national limit. Look for the junctions, look for cops, look for crap on the road, look out for squids riding it too: they sometimes cross the centreline oncoming. When you're sure, try it out, it's a lot of fun: but don't wind up in the Newspaper.
Not breathtaking but if you live nearby well worth a go. Just a couple of miles with half a dozen excellent bends. If you want to make it longer, go round the Thame ring road and follow B4011 through long crendon to Bicester.
Great road for going top whack on a sunday morning. 3 lanes of good surface and no cops ( commuted for a year including weekends), very wide but not twisty. goes 2 lane before bas but few entry/exits so easy to watch for trouble. Don't know their unmarked cars (yet) londoners - enjoy
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