During the Scottish Reformation, Robert Melville sided with the Protestant Lords of the Congregation. He was sent to England as a diplomat by Mary, Queen of Scots. He opposed her marriage to Henry, Lord Darnley and joined the rebellion called the Chaseabout Raid. Melville was sent to Elizabeth I of England as the rebel lords' envoy. He was forgiven by Mary and sent again to the English court as her diplomat. Mary expelled the English diplomat Thomas Randolph and Elizabeth ordered Melville's return to Scotland on 15 March 1566. He arrived in Edinburgh and reported back to Elizabeth and Cecil on the aftermath of the murder of David Rizzio. When Mary was captured at the battle of Carberry, Melville took Elizabeth's letters to her at Lochleven Castle and brought her requests to the Confederate Lords and her supporters. On the day that James VI of Scotland was crowned he wrote to Elizabeth that her ambassador Nicolas Throckmorton had helped defuse the situation and save Mary's life. Melville worked for Regent Moray, and arranged with Sir Valentine Browne, treasurer of Berwick, for loans of money secured with pledges of Mary's jewels. However he supported Mary at the Battle of Langside in 1568. After Mary fled to England he brought jewels, clothing, and horses to her at Bolton Castle. Subsequently, he joined his nephew William Kirkcaldy of Grange who held Edinburgh Castle for Mary. At the end of the "lang siege" of the castle he was imprisoned at Holyroodhouse and at Lethington Castle While awaiting his "examination", a kind of interrogation, in September 1573, he wrote to the English diplomat Henry Killigrew and Cecil for help. Melville said his enemies were destroying his reputation, saying that he had hindered peace, and knew all the secret dealings between France, England and Scotland. He said he had never been happy to receive help from Flanders. Melville hoped for English political intervention for his release. On 19 October 1573 Melville was questioned about negotiations for the marriage of Mary Queen of Scots to John of Austria, her escape from Lochleven Castle, her good and jewels, her proposed marriage to Thomas Howard, 4th Duke of Norfolk, the siege of Edinburgh Castle and those who supplied it with silver or gave loans secured against pledges of Mary's jewels. In 1582 Melville was rehabilitated and gained a role in the Scottish exchequer as Treasurer-Depute. In 1587 he was sent to England with William Keith of Delny and the Master of Gray to intercede for Mary's life. Their speeches and manner of mediation was said to have been counter-productive. In the late 1580s James VI of Scotland asked him to help the printer Robert Waldegrave who was in trouble in England. He was Chancellor when James VI sailed to meet Anne of Denmark. On 11 May 1590 he hosted the Danish AdmiralPeder Munk at Rossend Castle at Burntisland. Munk was travelling to Falkland Palace to take sasine of Anne of Denmark's "morning gift". In July 1593 he was ambassador in London and had an audience with Elizabeth I of England. His mission was to collect a subsidy or annuity of £4,000 which Elizabeth gave to James VI, and ask for 34 elm tress for the king's garden. She later complained that Melville had spent half of the money in London for the king, rather than taking it back Scotland. In 1594 he was made a judge as Lord Murdocairnie. In 1616 he was made Lord Melville of Monimail.
