The two names on Reegan's van were originally to have been Progressive Launderers Ltd and Masons Bakery, but these were later changed to Hayhoe Launderers Ltd and Silcock Bakeries in honour of assistant floor manager Margot Hayhoe and director's assistant Pauline Silcock.
Caroline John was forced to wear a blonde wig for the scenes were Liz is pursued, which frizzed in the rain.
This episode was watched by 8 million viewers on its original transmission.
There was originally an army character named Lieutenant Pollard, who was removed from the script.
Professor Heldorf was initially a German scientist named Kuhn.