This episode takes place in Runnymede, England on June 14, 1215 and in Arizona in 1968.
John Crawford (King John) played 1st Gestapo Man on Art for Hogan's Sake (1966), which interfered with this show when they originally aired on December 30, 1966. Hogan's Heroes (2nd season) and The Time Tunnel were in time slot competition with each other throughout the 1966-7 season.
The Time Tunnel is famous for using stock footage from various movies to portray the historic events and past time periods seen in the episodes. However, this episode also makes good use of Franz Waxman's rousing score from Prince Valiant (1954). The episode's opening credits use a skillfully edited version of the movie's title theme, and later in the episode there are various action scenes which use the music from the spectacular battle in the 1954 adventure.
Per the title, Robin Hood is a legendary figure in English folklore based loosely on the Earl of Locksley. He was famous for robbing from the rich and giving to the poor and fighting the corruption of King John and the Sheriff of Nottingham.
Tony suggests that he and Doug go to Runnymead to meet the Barons. Nottingham to Runnymead is over 125 miles.