Scots. The secretary of John Knox, Richard Bannatyne wrote that Errington, who he called "Haringtoun", had also delivered messages from Queen Elizabeth to the castle, which gave the defenders some encouragement, and they received further offers by a messenger called Hope, sent from William Drury, Marshall of Berwick. English diplomacy, for a time, was content to deal with both sides. The struggle against Kirkcaldy to take the castle became known as the "Lang Siege". An English artillery force was brought to Scotland to capture the castle from the its defenders, known as "Castilians", led by William Drury. Errington was one his captains and negotiators. Before the English cannon arrived, Errington went to Edinburgh Castle on 4 March 1573 to discuss terms of surrender offered by the English ambassador, Henry Killigrew. On a second visit on 27 March he noted that the defences had been improved by earthworks and modifications to the Spur fortification. Drury sent a plan of the castle showing the new works lately seen by Errington to Cecil. Errington was appointed Provost Marshal of the force of Scotland with command of the artillery, despite competition for the office from Thomas Sutton, who was Master of the Ordnance in Berwick. Diplomacy He was sent into Scotland in July 1575 to discuss the Redeswire incident with Regent Morton. The border wardens Sir John Carmichael and Sir John Forster had fought on 7 July, and Errington was sent into Scotland following the instructions of Francis Walsingham sent to the gentleman porter of Berwick, Sir John Selby of Twizell. He carried a message from the diplomat Henry Killigrew that Queen Elizabeth was displeased with the detention of Francis Russell, a son of the Earl of Bedford and Forster and his men at Dalkeith Palace. Morton claimed he entertained them guests during the crisis. After their interview, Morton released the men at held at Dalkeith the next day, except the leaders Forster and Russell. In June 1579 he went into Scotland with Claude Nau, the secretary of Mary, Queen of Scots, sent as ambassador to her son, James VI of Scotland, instead of John Lesley, Bishop of Ross. However, the Scottish court at Stirling Castle would not allow Nau an audience, apparently because Mary's letter was addressed to James as her son, not to the "King of Scotland". Errington had no accrediting papers from Elizabeth. The Privy Council of Scotland issued a proclamation