It was an adaptation by John Bowen of Shakespeare's play Julius Caesar which was produced by Ronald Smedley.
The adaptation is listed as one of Bowen's achievements in his obituary in The Guardian newspaper[1] It was originally made in three parts for use with schools and colleges but it was shown again a year later on BBC 2 on 21 October 1974 in a single 90 minute slot.
In 1971, just two years previous to the first 1973 TV production of Heil Caesar, John Bowen also wrote seven episodes of the ITV series The Guardians which also had as a central theme the threat of military dictatorship, and which was also set in the then near near future of the 1980s.
The idea that modern Western European countries could be subject to military or authoritarian rule was clearly not a fanciful one at that time.
Portugal, Greece and Spain were all subject to one or both of those forms of rule in the early 1970s when The Guardians and Heil Caesar were both written and first broadcast.