From UMHC Hiking Guide
Introduction
The Yorkshire Three Peaks Walk takes in the summits of Pen-y-ghent, Whernside and Ingleborough. The usual route for this walk starts from Horton in Ribblesdale, climbing Ingleborough and Whernside before returning to Horton and climbing Pen-y-ghent.
This walk of approximately 24 miles is typically done as a challenge walk within 12 hours and is extremely popular. If you clock in and out at the Pen-y-Ghent Cafe in Horton in Ribblesdale you will be invited to join the "Three peaks of Yorkshire Club". It costs £5 to join and you get a certificate and a woven badge.
The club has done this a few times:- pictures here
Alternative Walks
While the above route is much the most normal one it is perhaps slightly dissatisfying to split such a walk into two parts. A more natural if longer route was suggested by AJBrown in Striding through Yorkshire where he advocates starting at Dent to take in the full length of Whernside before ending in Litton. This extends the walk to around thirty miles but the terrain and paths are good so this should still be possible within 12 hours. Indeed Brown recounts going a further ten miles from Litton to Kilsney!
Another alternative route is to go straight from Horton up Pen y Ghent, then across to Whernside via the Ribblehead Viaduct, and back via Ingleborough. This is best done in this direction, because part of the ascent of Ingleborough from Chapel-le-dale is steep and would be less pleasant in descent; also, the summit of Pen-y-Ghent is quickly reached from Horton and it is good for morale to "bag" a summit early in the walk. A relatively direct route, about 23 miles.
Alternative long distance walks in the dales can easily be generated by doing circuits of valleys for example Dent to Dent via Whernside, Gragereth and Combe hill.
Finally it is worth noting that Ingleborough has many geographical features that can easily repay several days exploration.
