Having never done any running, or long distance walking, I did the Keswick to Barrow walk.
We ran (jogged) the first twelve or so miles to Grasmere, then on to Red Bank. Felt pretty good, (obviously my endurance is pretty reasonable from lots of cycling) and I thought “bloody hell, I’ll probably be finished soon, might get under seven hours.”
Walked up Red Bank, and then it was coming down the other side I realised my legs weren’t right. My hip flexors (I think) were really painful and I was struggling to walk; infact it was easier to sort of fall forwards and put my foot out to stop myself, rather than walking normally. Did the remaining 30 miles in this fashion.
Finished it in nine hours something. Could barely get into the car afterwards (thankfully I wasn’t driving). Fell out of the car into Tesco’s car park; had to use a shopping trolley as a walking aid to get across the car park to the shops. Got into the shops and near enough blacked out from the pain; have never felt anything like it, and probably will never again.
So, I reckon you can do it. But my advice would be: get your legs used to running and do some hip flexor stretches.