Sat Nav-ing

Today, as practice for needing to rely on a sat nav in the near future, the fly plugged one into the Pooh-mobile and set out.  (Sat nav kindly lent by the Richmond Residents - danke).  My scepticism is confounded - it took me there and back again.  The interesting thing is that it did not use the same route in reverse for the return journey.  Why would that be?  I did get to see more of suburbia however.