I've tried three times and I haven't completed it in any of them. The second time I'm sure I was on time, yet I failed. I did some Googleing and found I wasn't the only one with this problem and the suggestion was to drive slightly above the speed limit, but not so much that you got penalised for it. This I just did, and I arrived at Darlington in plenty of time (I was early) and yet I still failed!