Dodmore Cotton was the third son of Sir Robert Cotton and Elizabeth, daughter of John Dormer. He matriculated from King's College, Cambridge in 1607, and that he was admitted to Lincoln's Inn Court in November 1608.
At court Dodmore obtained a position as a gentleman of the King's privy chamber, and so was well known to King Charles I when he was appointed ambassador to King Abbas I of Persia in 1627. He sailed in March in the Rose, an East Indiaman, for Gombrun (Bandar Abbas), in the Persian Gulf. He was accompanied by Thomas Herbert, Naqd Ali Beg (the former Persian ambassador to the Court of Saint James), and Sir Robert Shirley (an English advisor to Naqd Ali Beg).
During the voyage Beg who's ambassadorship in London had been a failure committed suicide. After touching at the Cape of Good Hope, Madagascar, and Swali in Surat, the three Englishmen arrived in Gombrun on 10 January 1628. Cotton, with Herbert and Shirley in his train, then proceeded to Ashraff,[b] where he had an audience with King Abbas I. They then visited Mount Taurus and Casbin (Qazvin), where Shirley and Cotton died.
- At the time crowns of England Scotland and Ireland were in a personal union. However James I and Charles I styled themselves King of Great Britain and Ireland, and so the ambassador represented the interests of Charles as Sovereign of all three countries.
- In 1832 David Brewster wrote in The Edinburgh Encyclopædia that "Ashraff is celebrated as the favourite residence of Shah Abbas, and enjoys the only good harbour on the southern side of the Caspian. A description of the palace is given by Hanway, but it is now in ruins".(Brewster 1832, p. 461)
- Brewster, David, ed. (1832). "Persia: Mazenderan". The Edinburgh Encyclopædia. 15. J. and E. Parker. p. 461.
- Herbert, Thomas (2004). Foster, William, ed. Travels in Persia: 1627-1629. Routledge. p. 17. ISBN 9781134285846.
- MacLean, Gerald; Matar, Nabil (2011). Britain and the Islamic World, 1558-1713. Oxford University Press. pp. 66–67. ISBN 9780191619908.
- St. George, Sir Henry (1840). Phillipps, sir Thomas, ed. The Cambridgeshire visitation, 1619. p. 11.
- This article incorporates text from a publication now in the public domain: Firth, Charles Harding (1890). "Hacker, Francis". In Stephen, Leslie; Lee, Sidney. Dictionary of National Biography. 23. London: Smith, Elder & Co. pp. 416–418.