Who is Ewen Burton-Angus from Night Probe! and what is their importance?

Ewen Burton-Angus is a lieutenant in the British navy. He is assigned as a naval attaché at the British Embassy in Washington. Ewen learns about the North American Treaty from Jack Murphy, and he says that he will have it checked in England. His inquiry alerts the British to the treaty, and in response, they bring a former intelligence agent out of retirement to watch the Americans and to keep them from finding it. He meets the agent, Brian Shaw, at the airport when he arrives in the United States, and he sends him to Los Angeles to talk to Heidi in order to obtain information about the treaty. Burton-Angus is present at the quarry, and he is killed during the gunfire exchanged between the American and British marines.