20th century had many examples of mistaken groupthink at the top of government. Perhaps the worst was in the late 1930s when most of the great and good favoured appeasement of growing Germany military power. The majority of the Britain’s key opinion-formers and decision-makers were opposed to rearmament until March 1939, when Hitler’s invasion of Czechoslovakia showed that they had been wrong. A Westminster-Whitehall consensus was backed by the elite media, notably The Times newspaper and the BBC.

To assimilate parliament with the civil service as if they were a uniform governing class, and to bracket both with such purported champions of independent expression as The Times and the BBC, may seem to over-egg the historical record. Were our rulers so dull that they could not appreciate many sides to the argument and allow the occasional dissident? And are they still so today? Arguably, Establishment groupthink has been a problem in recent years with the debate on UK membership of the EU. It was certainly a problem in Britain’s relationship with Europe in the late 1930s. All of the Foreign Office ministers, the prime minister plus his key staff, The Times and the BBC misinterpreted people and events, and committed gross errors in policy appraisal.

During Lord Halifax’s fateful period as foreign secretary (February 1938-December 1940), his under-secretary was Richard (“Rab”) …