4 completed the route, but only 2 of those finishers actually came in before the 5pm cut off! I headed home at 4ish (I did the medium but retired halfway round due to injury - a good day out nonetheless), but I assume the usual 5pm course closure time was waived this year?

I don't think the conditions were what caused the issues with the Classic - I was up on Crinkle Crags when the thunderstorm hit and it made conditions slippy, but not too bad. The cloud mostly remained high/intermittent, so nav wasn't as challenging as it could have been. (Admittedly a lot of this will depend on your exact location when the weather hits.)

The retirement rate was quite a bit higher than normal for all three courses this year, but the Classic was particularly striking.

I think the route for the Classic was probably just too big for most of the field to have had a chance of completing it in time. It was a fair bit more distance and more ascent than usual, and the terrain in that area is really tough. My husband usually does the classic and he retired when he realised that he had no chance of making the cutoffs - he only went to CP3/4 and back to base, but still covered 35km. In a lot of years, 35km would cover the whole classic course.