What nobody seems to have mentioned (unless I missed it) is that for Prommers who arrive by car (and don't go Boo, Hiss - it is necessary for some, especially those doing the east-west routes rather than the north-south ones

) the change to a 20-minute cutoff makes it virtually impossible to get into a popular weekday 7 pm-start programme. By the time you've found a post-6.30 parking space where you can park free of charge, and hoofed it back to the Hall, it's almost certain to be later than 6.40, and it's back of the day queue for you, mate! If you start paying for parking, even Promming can start to get very expensive.
And that reminds me of something I have to go and look for ...