Douglas ' seal is on the Treaty of Salisbury approving the putative marriage between Margaret , Maid of Norway with Edward of Caernarfon .
Was amongst those nobles that hammered out the deal that would become the Treaty of Birgham .
Douglas ' seal is on the Treaty of Salisbury approving the putative marriage between Margaret , Maid of Norway with Edward of Caernarfon , and was amongst those nobles that hammered out the deal that would become the Treaty of Birgham .