我也没有标准答案，我觉得这里No.10 refer to唐宁街10号，又指首相的道歉

10 Downing Street ( [About this sound] pronunciation (help·info)) in London, also known colloquially in the United Kingdom as Number 10, is the official residence and executive office of the First Lord of the Treasury, usually also the prime minister.[2] Along with the adjoining Cabinet Office at 70 Whitehall, it is the headquarters of the Government of the United Kingdom.