Tate Modern is proposing a £165 million extension. Why? “Tate Modern has been a victim of its own extraordinary success. On all too many weekends, it can feel like a surreal cross between some brutalist shopping mall, Piranesian airport lounge and the Seven Circles of Hell. Deadly queues form for its hard-pressed cafes and lavatories. The bookshop can resemble a jumble sale. The galleries are often little more, for all their lofty grandeur, than corridors for crowds to tramp through in search of novelty, rarely stopping to look at the art on display.”