So, you are on your driving test, taking directions from a sat nav, approaching a large multi-lane roundabout and the sat nav says “cross the roundabout and take the fourth exit”, which happens to be right. To your horror, you find yourself in the left lane on approach. What with the stress of the test and all that, there was insufficient brain capcity to work out which lane you needed.

What do you do? (a) Join the roundabout, check your right mirror, then switch lanes to the correct one for the fourth exit hoping the examiner wouldn’t see or (b) Take the first exit contrary to what the sat nav is telling you.

Well I can tell you as a fact, that choosing (a) will result in a serious fault and a driving test failure, whereas choosing (b) will get you a minor if you are unlucky. Without a doubt, if you are in the wrong lane, then go the wrong way. The sat nav or the examiner will re-direct and you will not pick up a serious fault. Switch lanes and you will fail.