 In 1406 he was one of the commissioners sent to Charles, King of France, in order to renew the alliance with France against the English.He attended the General Council at Perth in 1415, and from September 1420 until his death four years later, William was Lord Chancellor of Scotland.On 9 August 1423 he was named First Commissioner to treat with England for the ransom of James I, which was accomplished the following year.