I wasn't aiming for a fast time; I'd already done a 7k+ session with my Sunday morning running group and this was simply a solo after-group session that has become my traditional "scenic route" home from the park where the sessions are held.
The route is one that I have run many times (although usually in the other direction); a mixture of roughish forest path and hard packed dirt former railway foot/cycle/bridle path. I wasn't putting any real effort into it; just simply zoning out, plodding along enjoying my surroundings. I wasn't paying any attention to the timings when each kilometre split buzzed on my wrist.
The was no "pressure" on me to achieve a particular time, pace or distance. The thing with doing a route that is effectively a commute between where I am and home, that familiarity means I know the distance of, is that there was never any need to check my progress; I knew the route and I knew where it would take me, so off I went.
5km later and it's only when I look at it on Strava that I notice; adding a nice surprise to what had been a relaxed run that had been completely unnotable in every way.