Corrected entry: A calendar seen in the story is for February 1972. (It is a leap year...there are 29 days on the calendar, and February only has 29 days once every four years). However, an ambulance seen later in the same story has an "L" suffix on its licence plate. "L" suffixes were only issued for the period 1 August 1972 to 31 July 1973, so the calendar must be months out of date...
Corrected entry: When Jo is calling for help she keeps saying "Calling Greyhound One..." then when Benton answers he says "Station to Greyhound One."...so which one of them is "Greyhound One", Jo - or Benton?
Correction: Answer: neither of them. The callsign 'Greyhound One' is actually the callsign of Brigadier Lethbridge-Stewart, who uses it in at least two stories ('Invasion of the Dinosaurs' and Season 25's story 'Battlefield'). So why is Benton answering using the Brigardier's callsign? Hasn't he got one of his own? Perhaps that's another error althogether...
Correction: Maybe no-one remembered to turn the calendar to the new month?