(written from a Production point of view)
John Abbott (born John Kefford) (5 June 1905 – 24 May 1996; age 90) was an English actor who worked steadily from the thirties to the eighties, amassing dozens of television guest appearances, and movie roles – almost a hundred and fifty total. He was particularly active in sixties television, with guest appearances in many of the shows of that era.
He lent a quiet dignity to the roles he played, even in relatively weak plots like Lost in Space. According to William Blackburn, Abbott was a very professional, Shakespeare-trained classic actor. (Star Trek: The Original Series HD DVD Special Features)