LONDON — Increasingly, Muslim women in Britain take their children to school and run errands covered head to toe in flowing black gowns that allow only a slit for their eyes. Like little else, their appearance has unnerved Britons, testing the limits of tolerance in this stridently secular nation. Many veiled women say they are targets of abuse. At the same time, efforts are growing to place legal curbs on the full Muslim veil, known as the niqab. The past year has seen numerous examples: A lawyer dressed in a niqab was told by an immigration judge that she could not represent a client because, he said, he could not hear her. A teacher wearing a niqab was told by a provincial school to go home. A student who was barred from wearing a niqab took her case to the courts, and lost. In fact, the British education authorities are proposing a ban on the niqab in schools altogether. David Sexton, a columnist for The Evening Standard, wrote recently that Britain has been ‘too deferential’ toward the veil. ‘I find such garb, in the context of a London street, first ridiculous and then directly offensive,’ he said. […]