the one i found down grizedale the other week!
Started off with a small bog
Then a few medium paced messy corners
Followed by what felt like miles and miles of roots, not just a few isolated twigs, a whole hillside covered in roots as thick as my arms and legs and a track worn over/through/arround them!
Before being spat out onto a stupidly fast gravel section i'd ridden before, the only limit to speed is how many corners you dare let off the brakes before untill the sensible part of your brain tells you that there could well be a walker/dog/drystone wall/slippery wooden bridge arround the corner (all were found!)
Seemed to be everything a trail center isn't condensed into 3 miles of singletrack!
To find it look for the bridleway going through "lawsons park"