I can't help feeling the concert promoters are also culpable. You'd think - with this being the first concert at the stadium - they'd have done their homework with regards to ensuring there was enough transport to cope with the volume of punters.
I do not agree. Reading between the lines the promoters feel let down by both Southern and the BTP's attitude. Personally I really do not think it is too unreasonable to expect scheduled trains to run. This is primarily what most are asking for.
As I mentioned, given the promoters are paying over 50k for transport (the main plank of this is between 50-60 buses continually shuttling between the city centre and the AMEX) hiring a few extra Southern goons to man the gates is a drop in the ocean. I understand the maximum load for the trains will be small but something is better than nothing.