Percy Clinton Sydney Smythe, 6th Viscount Strangford GCB GCH (31 August 1780 – 29 May 1855) was an Anglo-Irish diplomat.
He was the son of Lionel Smythe, 5th Viscount Strangford (1753–1801) and Maria Eliza Philipse. In 1769, his sixteen-year-old father left Ireland, joined the army and served during the American War of Independence. While quartered in New York in the winter of 1776 to 1777, he met and courted Maria. She was the daughter of Frederick Philipse III (1720–1785), the third and last Lord of Philipsburg Manor and a descendant of the Dutch founder of the city. At first, her father rejected Lionel, however, as Philipse was a Loyalist during the war, the New York Legislature confiscated his estate, one of the largest in the province, and Philipse changed his mind. They married in September 1779 at Trinity Church in Manhattan and they returned to the United Kingdom. Upon the withdrawal of the British troops from New York in 1783, Philipse also went to England, where he later died.
Smythe was educated at Harrow and graduated from Trinity College, Dublin in 1800, entered the diplomatic service, and in the following year succeeded to the title of Viscount Strangford in the Peerage of Ireland.
In 1806, he served as chargé d'affaires under the Earl of Rosslyn and the Earl of St Vincent, the Extraordinary Envoys of the United Kingdom to Portugal. In 1807, he was appointed British Envoy Extraordinary and Minister Plenipotentiary to Portugal under the reign of King George III. In 1807, as Britain's envoy to Portugal, Lord Strangford coordinated the Portuguese royal family's flight from Portugal to Brazil. Lord Clinton, as he was known in Brazil, he arrived with the Royal Family in Salvador in January 1808 and soon they moved to Rio de Janeiro where they arrived on March 8, 1808. Lord Clinton and the Brazilian accountant Dom Fernando José de Portugal had a hard work to do in the Brazilian Imperial Palace. They had to raise the money moved from Portugal to Brazil under the English escort. Their work was during thirty days. The tax service of 2% was according the Prize Money (the law had been canceled in 1803 and was re-edited in 1807). They counted one hundred million Pounds and two million pounds in taxes. (In that year, with that money would be possible to buy two hundred million bags of coffee, nowadays it is U$20 billion). After that, the payment delayed fourteen years to be paid after the English recognizance of the Brazilian Independence. That was the money Napoleon wanted to finance his war against England. Napoleon said in his memoirs that Don Jon was the only one to trick him.