Matthew Stewart, Regent Lennox died from a gunshot wound after a struggle on the streets of Stirling. On 18 November 1571, the new Regent, John Erskine, Earl of Mar, sent Morton with Robert Pitcairn, Commendator of Dunfermline and James MacGill of Nether Rankeillour to negotiate with Elizabeth's representative Henry Carey, 1st Baron Hunsdon, Governor of Berwick upon Tweed. Mar wanted English help to capture Edinburgh Castle from Sir William Kirkcaldy of Grange who held it for Mary, Queen of Scots. Regent Mar hoped that Morton could arrange for 12 cannons, 3000 foot soldiers, and wages for the 800 Scottish foot soldiers and 200 horsemen already in the field. Morton was instructed to offer six hostages to England from the sons of the nobility who supported James VI. He also discussed returning the Earl of Northumberland to England who was a fugitive after the failed Rising of the North.