Sacred monster. This year’s Proms season began with the Mahler Eighth, which is like having the Queen Mary tootle up the Thames for the first day of Henley. (To let us down gently, we get Die Meistersinger tomorrow night and Simon Boccanegra the night after that – no musician in London will go without a paycheck this week.) In the bad old days all of Mahler’s symphonies were accused of being freakishly outsized, but only this one, to my mind, qualifies. One longs for it to be smaller, even when the chorus is only six hundred strong, as it was last night, well short of the eight hundred or so it would take to qualify as the “Symphony of a Thousand” – to be fair, the nickname was added by an imaginative impressario. The symphony has trouble getting ashore, but worse than that, Mahler’s conception is self-defeating.