The producer
If there's just one reason for The World at War's enduring appeal, then that reason is the programme's producer, Jeremy Isaacs. Isaacs had to do a major persuasion job on Thames Television to get the series made in the first place. Large-scale, historical projects (26, 50-minute episodes to be shown once a week over six months) were not a natural programming choice for a commercial broadcaster in the early 1970s. Once he got the go-ahead, he poured all of his considerable energy into making a piece of television that would never be forgotten. His first job was to pull together the best production team he could. The result was a multi-talented line-up that included David Elstein, who later became chief executive at Channel 5, Ted Childs, who went on to produce top-drawer dramas such as The Sweeney and Inspector Morse, and Charles Douglas-Home, who became editor of The Times. Of course, Isaacs himself was destined for senior positions in media and the arts, too: he was Channels 4's first chief executive and went on to become the director of the Royal Opera House. He was knighted in 1996.

The vision
Isaacs didn't want a dull trudge through military history. He wanted a story that reflected the all-embracing nature of the conflict as it affected all those - especially Britons - who lived through it. There were three million feet of archive film to draw upon but he needed a structure to make sense of the countless battles recorded. Together with historical adviser Noble Frankland, he picked 15 key military campaigns to focus on. The rest of series was devoted to programmes that would put that fighting into context. The result was a finely judged mix of military campaigns, politics and the civilian experience.

The writing
"Down this road, on a summer's day in 1944, the soldiers came. Nobody lives here now. They stayed only a few hours. When they had gone, a community which had lived for a thousand years was dead." With these lines, The World at War opens. The writing stays this good all the way through - spare, focused, emotive without being mawkish. But The World at War didn't just have a great script. It had a great narrator, too. Sir Laurence Olivier approached the job as if he were delivering a Shakespearean speech, finding nuances in the tautly written script to enrich and heighten the true-life dramas he was narrating.

The score
Another vital component of The World at War was its haunting theme, composed by Carl Davis. New Yorker Davis moved to the UK in 1961 and became renowned for his imaginative scoring across a range of television programmes, including Up Pompeii, The Naked Civil Servant, Private Schultz, A Year in Provence and Pride and Prejudice. His film credits include The French Lieutenant's Woman and Topsy-Turvy. The programme's haunting title sequence - a series of dissolving images, intercut with flames and set to the Davis score - took weeks to perfect.

The people
The World at War had many strengths but the key to its success as compelling history television was the formidable array of interviewees. Top military leaders, including German naval commander Karl Doenitz and the head of RAF Bomber Command, Arthur Harris, had their say alongside humble soldiers, sailors and airmen. Key politicians like wartime foreign secretary Sir Anthony Eden shed light on the war's wider arc, while ordinary citizens told of events from their perspective. Several members of Hitler's inner circle were also tracked down and interviewed, including his valet, secretary and adjutant. Death camp survivors told their terrible tales, as did a few of their shamefaced captors. More years have now passed since the making of The World at War than elapsed between 1945 and the programme's first showing in 1973. So, sadly, a programme like this can never be made again: the number of living witnesses to World War II is dwindling every day. We are fortunate that Isaacs and his team had the vision and talent to make The World at War when they did.