Despite being the main guest star of the serial, The Monitor does not turn up until halfway through the second part of the serial.
The role of The Monitor was written for a 60 year old man, the actor cast John Fraser was 49 years old.
This episode was watched by 7.7 million viewers on its original transmission.
According to Christopher H. Bidmead, the Logopolitans employ a hexadecimal, or base-16, numerical system, a real system commonly used in computer programming. When Adric and the Monitor read strings of numbers and letters, the letters are actually the numbers between 10 and 15, expressed as single digits.