Theresa May is to give further details of her plans for Brexit in a speech in which she will declare she does not want an outcome which leaves the UK “half-in, half-out” of the European Union. Extracts released by Downing Street in advance of the much-awaited address are likely to fuel speculation that the Prime Minister is ready to take Britain out of the European single market and customs union, though it remained unclear whether she will give a definitive answer on the question.