He was a general in the army and fought in the War of the Spanish Succession and also served as Ambassador to the Netherlands and as Master-General of the Ordnance.

In 1716, he was raised to the Peerage of Great Britain as Baron Cadogan, of Reading in the County of Berkshire, with normal remainder to the heirs male of his body.

Cadogan married Elizabeth, second daughter and heiress of the prominent physician and collector Sir Hans Sloane.

In 1831, one year before he succeeded in the earldom, he was raised to the Peerage of the United Kingdom in his own right as Baron Oakley, of Caversham in the County of Oxford.

His second son Henry Cadogan, Viscount Chelsea, heir apparent to the earldom from 1878 to 1908, represented Bury St Edmunds in Parliament as a Conservative, but died in 1908, seven years before his father.

[n 1] Sir Alexander Cadogan, eighth and youngest son of the fifth Earl, was the most senior civil servant to a troubled government department (Permanent Under-Secretary for Foreign Affairs) between 1938 and 1946, that of World War II and his personal notes reflect his part in shaping the policies which aided the survival of Britain and its British Empire's resources in Asia during that war.

[3] The Earls Cadogan are wealthy landowners, having planned and developed and still owning Cadogan Estates, which covers much of Chelsea and parts of the much smaller area of Knightsbridge, and second only to the Duke of Westminster as Central London's richest landlords (whose surname, Grosvenor, is also closely associated with some of the most ornate London architecture).

[4] The heir apparent is the present holder's eldest son George Edward Charles Diether Cadogan, Viscount Chelsea (b.