At the time i was in my 20,s,an extremely fit guy with an extremely fit bulldog pulling me along,i couldnt have walked any faster without running....measure out an exact mile and try it,...
World class race walkers can do it in around 8 minutes,but of course they are virtually running and only technique means they can " walk " at that pace......for the normal everyday joe you can safely double that time.
10min mileing is some going,use to do 10mile in 1.40 with weight when in army ,but that was with a lot of running and the walk was like a slow jog ,so without weight and no running 14min