About five or six minutes. An average walking speed is 4 mph...ie 7040 yards per hour...so covering around 700 yards (about 1/10th of that distance) should take 1/10th of an hour.
Whilst I won't dispute QMs calcs, the average walking speed is 5km per hour so that's 1km every 12 minutes so effectively you could walk, in a straight line on a level plain with no traffic lights(!) in about 7.8 minutes ...