By a bizarre coincidence, actor Anthony Andrews was jotting down some thoughts for a series about wartime bomb-disposal officers when producer John Hawkesworth telephoned him and, out of the blue, offered him the role of Brian Ash in Danger UXB (1979).
The 'Butterfly Winter' story (episode 10) was loosely based on a true story. In reality the Luftwaffe dropped the 'Butterfly Bomb' (officially known as the SD2) on the towns of Ipswich, Grimsby, Hull and Cleethorpes, and on the island of Malta, but not in the south east as depicted in this episode. They were lethal 2kg cluster bombs that were not designed to go off on impact but rather were either on a pre-set timer or were triggered if they were disturbed. Unfortunately many small children were killed or injured by them when they picked them up thinking they were toys. The Butterfly bomb was as disruptive as it was nasty, and particularly difficult to deal with. Many if not most of them that had not already detonated were set off in a controlled explosion as they were too fiddly and unpredictable to be defused. Due to the disruption they caused the War Office issued a 'D notice' which requested the British press do not report on raids where these were used. The hope was that by not mentioning it, the German spy network would not mention it in reports and therefore the Luftwaffe would consider the bombs to have been relatively ineffective and be discouraged from using them in future. The plan worked as the bombs were not dropped on any of the major inland cities in Britain.
Most location filming was done in the Streatham, Tooting and Clapham areas of London. At the time of filming, in 1978, some old pre WW2 houses were in the process of being pulled down to make way for modern housing so there was a bit of a rush on to film in these older areas before they were gone for good. Some use of Surrey countryside was made for a few shots and scenes (filmed on the outskirts of Guildford which back then still had quite a bit of farm land surrounding it).
Anthony Andrews was the original choice to play 'Bodie' in the ITV television series 'The Professionals' (1977-1982). However he was sacked just two days into filming the pilot show as the producer felt that he was a wrong fit for the role and he was replaced by Lewis Collins. However his sacking proved to be unexpectedly fortuitous as it made him available to take the lead role of Brian Ash when this show was being cast a few months later.
The series was produced by "Euston Films," who were a production house for the ITV network in the UK. After the cancellation of the series 'The Sweeney' in 1978, "Euston Films" were looking for a new project to work on and this was the end result. After this series ended, "Euston Films" went straight on to make the classic comedy/drama 'Minder' which ran for ten years and then was briefly revived in the mid 1990s.