Your driving test result is based on what the DSA driving examiner observers during the 40 minutes of the practical car assessment and has been marked on the DL25 report sheet in real time. At the end of the assessment in test centre car park all the examiner does is add up the number of driving errors commited and takes note of any serious or dangerous mistakes made.
You will pass the driving test if you have made less than 16 minor error and no serious or dangerous errors as shown on the test report sheet. The examiner does not change a minor error to a major just to fail you (to meet the mythical driving test quota), nor do they invent a major mistake from nowhere. While there have been cases where examiners have been harsh with decisions (awarding a serious for something that could have been a minor), usually there was a fault committed, and it is down to the examiner's interpretation of the events.
I've sat in the back of the car on many driving tests as an instructor, and have not yet disagreed with any cases where my learners have been failed, so all I can say is take your driving lessons very serious, in particular deal with any repeated errors that you keep making, especially on your driving maneuvers, as any one of these could affect your driving test result.
If you don't give the examiner an excuse to put a mark on the dsa DL25 report sheet, then you have a higher chance of getting the driving test result that you desire, a pass.
Everyday there is someone in the UK that passes with no errors on their test, so practice until you've got it all nailed and in the bag.
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