Vaughan was educated at Rugby School, where he entered on 22 January 1788, and at Merton College, Oxford, matriculating on 26 October 1791.
The following year, he made his way from Aleppo to Persia, fell ill near the Caspian Sea, and was indebted perhaps for his life to the kindness of some Russian officers.
With them, he sailed for the Volga in November, was shut out by the ice, and had to spend the winter on the desert island of Kulali, but eventually arrived at Astrakhan in April 1806, reaching England by way of St Petersburg on 11 August 1806.
He acted as minister-plenipotentiary during the absence of his chief from August 1815 until December 1816, and his correspondence during these years throws much light on Spanish politics.
On 5 April 1820, he went to Paris as secretary of embassy under his old friend Sir Charles Stuart, and on 8 February 1823, became minister-plenipotentiary to the confederated states of Switzerland.
Though, in Sir Charles Webster's view, a man of 'no great ability', he dealt with important matters such as the Canadian boundary, the Latin American republics, the slave trade, and the tariff.