This Is Still Not a PipeThe Afterlife of MagritteGagosian, Grosvenor Hill, London⭑⭑⭑⭑⭑IT’S SATURDAY mid-afternoon and there’s an unexpected 30-deep queue outside the gallery that’s neatly secluded in the otherwise deserted mews in this Georgian/neoclassical part of town. We will be ushered in, free of charge, in twos and threes as earlier admissions leave with their furrowed brows and distant looks in their eyes, glazed by Magritte’s visions.