And so the great day has come. The frantic checking of every detail of the preparations; the terror that something may have been forgotten and will create a huge public embarrassment, detracting from the dignity of the great occasion-major State Visits are a gruelling affair for the officials involved. After twenty years in the British Diplomatic Service I remember this well.

But at least the atmosphere is good; 2015 has been a good year for Sino-British relations. Earlier in the year Britain sent a strong signal to China that we are making a serious effort to seek common ground for cooperation, by taking the initiative in indicating willingness to sign up for the AIIB project, in the face of opposition from our US allies. Both sides have expressed happiness with recent progress; Chinese officials have been talking about a "golden period", even a "golden decade", in bilateral relations. Prince William has visited China to symbolise Britain's ongoing commitment to the relationship, as he is likely to be our Head of State for decades to come. As regards practical cooperation, the Chancellor of the Exchequer George Osborne has paid a valuable advance visit to China, hoping to agree some joint projects in principle which will form part of the achievements of the big occasion. And now the highest level in British ceremonial has begun, as President Xi Jinping arrives in Britain for a full State Visit, during which the Chinese leader will be received by the Queen and will stay at Buckingham Palace.

The nineteenth-century English political philosopher Walter Bagehot analysed the (famously unwritten) British constitution, and found that the functions of state fall into two parts: the 'dignified' and 'efficient' aspects of governance. The 'efficient' part deals with the practical operations of government, economic management and the fine details of the rule of law, but the 'dignified' part is equally important for the running of a State. China has always understood this as well as Britain, from Imperial times until today; the State needs at times to underpin its authority and prestige by means of a demonstration of showmanship. China demonstrated this aspect of governance recently in the powerfully expressed commemoration of the seventieth anniversary of the Allied victory in World War II. And now Britain is demonstrating her own version of high ceremony in President Xi's reception as the Queen's guest. We know that the British style of ceremony tends to be more old-fashioned in tone than that of China, which is peculiar, considering that China's civilisation is by far the older. But both countries do what they do very well and in a dignified manner. And no Head of State on earth has more experience in giving an appropriate welcome to another than Her Majesty the Queen, in her 64th year as Head of State.