This walk around Blagdon Lake (marked in green) is 11 miles. Follow the route clockwise starting at the Blagdon car park (marked (I) on the map). Assuming a 9.30am start, there are places marked for a morning snack and lunch. The first has great views over Blagdon Lake itself and the second overlooks Chew Valley Lake. There is only one climb, and that is near the end, going from near the lake to the outskirts of Blagdon. There is very little mud, and only one or two herds of cows, which can usually be avoided, as the fields are big.
Note: the route is quite complex, and finding the footpaths on each leg is not always straightforward. If you have this page open on a smartphone, it will show you where you are on the map. You can make it go full screen, and zoom in and out. Of course, there may not be full mobile phone coverage all the way round. Alternatively, if you have a GPS device or an offline map app on your phone, you can download the trail file (GPX, etc) from below and load the route into your device.