Sempill was Ambassador to
England in the years 1591-1600 and was
knighted on Christmas Day 1600. Another Scot employed by the King in London, James Hudson, referred to Sempill's youth and inexperience in March 1599. Hudson wrote that Sempill was "a raw piece to employ and one unskilful, only a scholar". The mission concerned the
Valentine Thomas affair and the rebel
Earl of Bothwell.
Roger Aston, an English courtier of James VI, wrote in August 1599 that "Beltries was plain and honest, and by the means of Sir
George Elphinstone (of
Blythswood) whose sister he married, he may do good offices." Hudson wrote again to
Sir Robert Cecil, the English
Secretary of State in September 1599, praising Sempill's good nature, and mentioning that his paternal grandmother was English. Hudson added that Sempill would be "the true Lord Sempill if he had his due." Sempill sent newsletters to Cecil, and in English correspondence he was known by the cipher "99". In August 1599, James Sempill was sent to London to take the place of
David Foulis and collect the
"gratuity" for James VI, a sum of money which
Elizabeth I of England sent to Scotland to support James VI. He delivered £400 sterling of this money to
George Heriot for jewels given as
New Year's Day gifts. A Scottish servant of
Lady Kildare named Dicksoun ingratiated himself with Sempill, and said she had spoken in favour of the king's succession to the English throne at dinner with the
Lord Admiral. He seems to have carried letters from
Anthony Bacon and the
Earl of Essex to
Lord Willoughby in January 1600. He obtained £3000 as subsidy for King James. On his return to Scotland, in April 1600, Anne of Denmark asked him what Elizabeth had said about her, and she disbelieved him at first, based on the reports of others. A joke was made about young
Prince Henry's involvement in diplomacy. Sempill was privy to correspondence between
Anne of Denmark and
Albert VII, Archduke of Austria. In December 1600, James gave him £100 sterling from the English subsidy to cover his previous expenses as a diplomat in England. Sempill became involved in the discussions following the kidnap of
Edmund Ashfield by English agent at
Leith. In 1601 he was sent to
France, and accompanied the
Duke of Lennox from Dieppe to London in October. In November 1601 the
Earl of Northampton wrote to the
Earl of Mar that in London the king's agent
James Hamilton stirred up
Frances Howard, Countess of Kildare, the Duke of Lennox, and Sempill, who 'like an organ, sowndes when the other blowes'. Back in Scotland, in April 1602 Anne of Denmark asked him to mention her in a letter to Robert Cecil. She told Sempill that Sir
Thomas Erskine of Gogar had been the author of slanders against her which were current in France and England. Erskine kept the King busy writing to England, and she wished she knew what these letters were about, and would have intercepted them if she could. She had had an offer from a courtier to destroy the career of the Earl of Mar if she undermined the Duke of Lennox, which she knew how to do, and understandably wanted Sempill to keep this secret. Sempill hoped Cecil would cut off this part of the letter and burn it. Sempill wrote to Cecil again in May 1602.
Marie Stewart, Countess of Mar had written to her brother the Duke of Lennox complaining he was the Earl of Mar's main opponent in Scotland. Sir Thomas Erskine was blamed for their trouble, and slanders against the Duke in France and England. On 3 February 1603 James gave him a
jewel which had belonged to Mary, Queen of Scots for his good service abroad and at home, and faithful conduct of diplomatic negotiations. The jewel was a carcatt (necklace chain) with a diamond in one piece and a ruby in another, with a tablet (locket) set with a carbuncle of a diamond and ruby, set around with diamonds. James Sempill of Beltrees died at Paisley in 1626. ==Works==