On 10 June Queen Elizabeth appointed him Clerk of the Ordnance, which displeased John Bennett, who had a similar role.
He advised Cecil to have the storehouses in Bennet's control secured from his wife and others, and offered to take on Bennett's responsibilities for only two shillings more pay weekly.
[3] In Scotland there was a civil war between the followers of Mary, Queen of Scots and the supporters of her son James VI.
Mary, Queen of Scots was informed of his activities and wrote in March 1571 about the man named "Arrington" or "Harrington" who had been sent by Elizabeth I and the Earl of Sussex to see Regent Lennox.
[4] On 27 April 1572 Errington delivered a letter to Regent Mar for Lord Hunsdon about the rendition of the Earl of Northumberland.
He described fighting on Edinburgh's Canongate, and the capture and execution of soldiers loyal to Mary, Queen of Scots, (at Cramond Bridge), who were going north to join with Adam Gordon of Auchindoun.
An English artillery force was brought to Scotland to capture the castle from its defenders, known as "Castilians", led by William Drury.
[11] 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.
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.
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".
[16] In November 1579 Errington was sent again to James VI, who was now officially the adult ruler of Scotland at age 14, to discuss the progress of border matters since 1572, the "Pacification of Perth", and retrospective justice or revocations especially concerning the Hamilton family.