James Somerville wrote to Queen Regent of Scotland, Mary of Guise, from Cowthally Castle on 22 March 1554.
On 10 May 1560, he signed the ratification of the Treaty of Berwick, by which the Lords of the Congregation invited the English army that was besieging Leith.
[2] With other Lords, Somerville signed three letters in support of the release of Mary, Queen of Scots from England.
Another letter on 30 July 1568 appealed to the Duke of Alba to get Spanish support for the release of Mary.
With no reply from Elizabeth, on 24 August Somerville signed another letter at Dumbarton Castle.