Great thread. I walk to keep fit as well as for pleasure. I also have a 27 year old elite athlete my son, as motivation. If I'm out basically training, then I will average 3 to 3.5 mph over 10 to 15 miles of typical moorland terrain including 3 to 4000 ft of ascent and descent. I am no runner but I am 6ft 4, so my long stride on flat ground and gentle descents makes up for the steeper sections.
Out with our ramblers walking group today we covered 17 miles, with 4350ft of ascents, in 7 hours including 3 stops. So 2.4 avearage. Age range in the group of 17, today included Ten tors challengers training for next weekend through to pentioners. In fact there was one young lad walking with his grandmother.
Out walking the coast path with my wife and daughter weekend before last, we covered, 5miles with 3520ft of ascents in 4.5 hours with plenty of stops for photos. So just over 1.1 mph average.
So horses for courses, you can walk as fast as you are able, or you can just walk as fast as you want to..