Follow Hannegan trail up to Hannegan Pass, then continue predominantly south to the north ridge of Ruth avoiding crevasses to the summit.  
 

https://www.summitpost.org/ruth-mountain/150890

A circular trail around Welwyn Garden City, It unites and encompasses the whole town, joining existing footpaths and rights of way into a beautiful 20.20km circular route.

With excellent access from London this is an interesting and fast trail route that opens up a new network of paths and trails