Just about, yes!
From London, we suggest flying to Glasgow (flight time 1 hour 15 minutes from London), then train to Fort William (last departure from Glasgow Queen Street is 6:23pm, at the time of writing in summer 2022). You'll be in Fort William soon after 10pm, ready to spend the night and meet us in town the following morning to start the challenge!
From Manchester, flight time to Inverness is 1 hour 20 minutes. The last CityLink bus from Inverness to Fort William departs at 8.15pm.