Background
He was born in London, the third son of an innkeeper, but orphaned at an early age.
He was born in London, the third son of an innkeeper, but orphaned at an early age.
He was educated at Christ"s Hospital and at Pembroke College, Cambridge.
In 1902 Christ"s Hospital named one of its boarding houses after him. He became British vice-consul in Maryland in June 1793 and was ambassador to the United States from 1800 to 1804. He was then posted to Sweden as minister-plenipotentiary in December 1807 with the objective of forming an alliance against Napoleon, returning to England in November 1808.
In October 1811 he went again to Sweden (until 1817) on a special mission in HMS Victory and he successfully negotiated treaties of alliance with both Sweden and Russia.
This was the first stage in the creation of an alliance of Northern European States against Napoleon. He was appointed minister to Portugal in July 1817 and joined the Portuguese court in Brazil.
He was ambassador to Portugal from April 1819 to March 1821, when he returned to England. Thornton was created count of Cassilhas in the Portuguese nobility by the King of Portugal.
He was elected a Fellow of the Royal Society in June 1810, appointed Knight Grand Cross of the Order of the Bath in 1822 and retired in August 1824.
In retirement he lived in Wembury House, Plymouth, Devon, where he died in 1852.
Royal Society]
He became a member of the Privy council in 1816.