Back in the dark ages I did O levels when all exams were 2.5 hours plus (I found my maths paper and it was 2 2.5 hour papers and I remember the rest being the same). A levels were 3 hours.
Now GCSE maths papers are 2 lots of 90 mins, and A levels seem to be 2 or 2.5 hours.
when did they change and why?