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This is a really varied trail route. It covers sweet singletrack descents through forest descents, open countryside farm land that goes on for miles and a few decent steep challenging climbs to keep the heart rate up. 

It is a tough route not because it is so technically demanding but more because of it's distance (It is 50k with 820 metres of climbing!) and it has some fun ambiguity in track direction. Good map reading or a handy GPS would be recommended. I closed the route at 54k being I went in the wrong direction for 2k and then tracked 2k back...but luckily just the once. Although the detour was a great track in itself;) 

I used the MRB route card as my initial guide (great these things to map out the route onto a decent sized Ordnance survey map). For me this was the OS Landranger Series (1:50,000) 175 Reading and Windsor as well as a little section of the 165 Aylesbury & Leyton Buzzard. 

You can park on the road or in  a small turning off the main road just in Nettlebed North of A4130 (OS175/SU70386). Then head down the hill to the main road and take the left to the roundabout. Then straight over for 700 meters and take the bridleway on the right. The route from here is a great taste of what is coming. Lovely little descent down. Go through the woods and at the bottom bear to your right then left onto a track. Turn right to go uphill at the first fork and then bear left at a X roads when you enter the woods. Turn left at a junction by the Estate office. I remember seeing a few similar options so good to check on compass here. Follow this track back into the woods. Continue until you get to the road.. turn right and continue down to the B491 where you turn left. 

 

Go down this road for 900 metres where you turn off right into a bridleway. Follow into the wood which drops sweetly to a fork at the bottom where you keep rightish (don't turn right) to climb up to a road.

Bear right for 500 metres and when the track bends right bear left onto a bridleway that climbs up into the woods. Then few hundred yards on take a right at top junction and continue through open land down across a track and straight across to a gate (of types!). Go through and take a sharp left turning up across the forest edge.. 400 metres on there is a junction just ahead of another road where you turn right to descend. Fork right immediately and drop steeply to road where you go straight across and up steep little little bit to a junction. 

 

You go straight across to farm buildings at Howberrywood and bear right around the buildings. You continue to a sharp right hand bend and bear left onto a bridleway descent that is fun. Continue through the woods to a drive by some houses and turn right to the road. Turn right and right again onto the A4130. Continue for 300 metres and turn left onto Huntercombe End Lane. Continue to a sharp right hand bend and turn left onto a bridleway. Follow this for 500m and bear left onto a narrow Bridleway that descends to a junction near buildings.

Bear half right onto a broad track and follow this to the top of the hill where you turn right onto another field edge bridleway. Keep straight ahead for 2 km to a Lane. 

  

Turn right then left onto the ridgeway and follow this for 8km, crossing three roads. At Xroads by M40, bear right to climb steeply to road at top and bear left towards motorway.

 

As you start by the bridge, bear right onto singletrack and follow this through a gate and down into the estate. Continue to a drive and bear right (Way marked Wormsley) and then after 500 metres where this goes right , bear left onto a bridleway 

 

Follow this to a fork to a fork at the foot of a wood and bear right to tarmac drive where you keep straight across onto a steep climb. Keep straight across as this turns into a drive and climb to farm. Keep straight across to the road.

Turn right for 600 metres and then bear left onto a narrow bridleway. Go left onto track and drop down through woods to a junction where you turn left. Follow this track past a large farm and down to the junction with the lane. Turn right then right again to Pishill. Continue onto the village where you turn left to climb up and around to the right. Continue to the farm and straight ahead on drive to the road. Turn left past the pond then right onto the bridleway and drop to the junction., Bear left and keep straight ahead for 300 metres. Continue down to a T Junction where you turn left to follow a major track down to a car park and road at Warburg. Turn right then right again onto a broad track. Climb keeping left,  uphill at a fork. Continue down to junction and bear right dropping back into Nettlebed.

If you are doing this with a GPS and don't get lost allow 5+ hours min. If map reading and having to stop to navigate add an extra hour.  Give another 30 mins for breaks etc and this is a full day out. Hence recommend either do in the summer or if in winter (where it gets quite muddy in the Chilterns) then get there early morning and enjoy the elements max style so you can maximise day light hours. 

Also recommend waterproof socks as there are some deep puddles on this route that look deceivingly shallow;)  

Tips:

Use the MRB map North From Henley, Chiltern hills. Map it out on a big scale map. check out the map reading posts. Take tons of water and energy supplements. Eat something little and often.  Isotonic type solutions are recommended. Check out the nutrition posts in the surgery section. Stretch afterwards (lots) and spen the last ten minutes doing anaerobic exercise to loosen up on your bike see recovery posts. Wear waterproof socks. Let others have a copy of your route card if you are riding alone.