The game is broken. Race time was 18:21:XXX on normal difficulty.
I could have gone faster but I've discovered a bit of a
trick with the AI so in the esses instead of being on the power in 2nd gear, I took them at a similar speed in 3rd. In fact most turns except the hairpin were taken in a less than optimal gear. I still hammered the straights and sections between corners.
I genuinely believe I can do it on RMs using the approach above. I'd have to treat it as 2 x 5 lap races, aiming to get to first at the end of each 5 lap stint.
That's my thinking. As per the linked post I've included above - the faster I (or you are clearly) driving, the more the AI cheats.
It's not ideal...but 17:45:XXX is insane with a pitstop.