The Reference Desk/American actors in Classic Who

Can anyone help me confirm that American actor Stubby Kaye was the first American actor to guest-star in Classic Who? He played 1960s CIA agent Weismuller in the 1987 7th Doctor serial "Delta and the Bannermen". However, the actor's entry here on this wiki just says he was one of the first, not the very first, and there's no indication as to whether or not actor Morgan K. Deare, who played the other CIA agent in Bannermen, is American also (imdb.com doesn't say either, and wikipedia has no entry on Deare).

So, was it Kaye, or did someone come before even him?