START on southbound sliproad to A41 on the Western Tring junction approx 40 yards from the start of the sliproad. Proceed along A41 to come off at first sliproad (Eastern Tring junction) to:- TURN (approx 2.0 miles) by taking 4th exit out of RAB and under the A41, going around 2nd RAB to take 2nd exit back onto the A41 westbound and continue past all junctions to RAB at end of Aston Clinton by-pass to:- TURN (7.87 miles) by taking 3rd exit out of RAB back along the by-pass, again ignoring College Road junction to:- FINISH on Buckland sliproad 9 yards south-east of manhole cover on grass verge, about 91 yards nth-west of (i.e. before) separation of slip road and main carriageway, also about 460 yards nth-west of the B489 overbridge.