The Most Distinguished Order of Saint Michael and Saint George is a British order of chivalry founded on 28 April 1818 by George, Prince Regent, later King George IV, while he was acting as regent for his father, King George III. 

It is named in honour of two military saints, St Michael and St George. 

The Order of St Michael and St George was originally awarded to those holding commands or high position in the Mediterranean territories acquired in the Napoleonic Wars, and was subsequently extended to holders of similar office or position in other territories of the British Empire. It is at present awarded to men and women who hold high office or who render extraordinary or important non-military service in a foreign country, and can also be conferred for important or loyal service in relation to foreign and Commonwealth affairs. 

The Order includes three classes, in descending order of seniority and rank: 

It is used to honour individuals who have rendered important services in relation to Commonwealth or foreign nations. People are appointed to the Order rather than awarded it. British Ambassadors to foreign nations are regularly appointed as KCMGs or CMGs. For example, the former British Ambassador to the United States, Sir David Manning, was appointed a CMG when he worked for the British Foreign and Commonwealth Office (FCO), and then after his appointment as British Ambassador to the US, he was promoted to a Knight Commander (KCMG). It is the traditional award for members of the FCO.
What was he given when he worked there?
was appointed a CMG when he worked for the British Foreign and Commonwealth Office (FCO