But in the stunned aftermath of 9/11 no-one could conceive of a time when some heartless Hollywood type would step forward and unveil plans to put the episode on celluloid. It was considered by so many to be untouchable: a sacred, taboo subject cloaked in national mourning that should not be sullied by commercialism.

Yet in less than four years, half a dozen separate projects were on the slate. Two docu-dramas, Paul Greengrass' Flight 93 and Oliver Stone's World Trade Center, focused on pride, heroism and survival. They cheered loudly for Uncle Sam and all he represented. Moreover, they proved that taboos can be broken.

The United States has travelled that stony road before. During the Vietnam War a stampede of pictures beat a frenzied path to cinema screens. Now, with the conflict in Iraq still quietly raging, a new breed of film has begun to creep into our multiplexes. It's all uncomfortably familiar, and carries echoes of the 1970s.

Things move much slower in the UK. It's taken nearly 40 years for the British public to accept dramatisations of the Moors Murders and their aftermath. Two have been made; more may yet happen.

For Vietnam, read Ulster. True, there have been films about the Troubles but two new titles look set to reignite memories of IRA terrorism.

The first is Hunger, a biopic of IRA hunger striker Bobby Sands, 27, who died in the H-block prison hospital at Long Kesh in 1981 after refusing food for 65 days.

Next is Fifty Dead Men Walking, a drama inspired by the real-life story of Martin McGartland, who was an undercover British spy in the IRA. What becomes clear is that some subjects become more acceptable as entertainment as the years wear on and memories fade.

After 40 years, maybe the Moors Murders have boiled down to those black-and-white images of two hard-faced people with cold, staring eyes. The victims' families would disagree.

Britain's ultimate taboo remains the Yorkshire Ripper.

Almost four decades have passed since Peter William Sutcliffe first raised his hammer. Like Ian Brady and Myra Hindley, he has become synonymous with a picture frozen in time: a wedding portrait of a saturnine, dead-eyed man smiling for the camera.

Nine years ago Granada Television produced This is Personal, a two-part look at the shambolic Ripper inquiry that centred on senior officers and the manhunt that scarred their lives.

Now a new TV drama, David Peace's Red Riding Quartet, is being shot in Yorkshire. Like its predecessor, it focuses not on Sutcliffe but on the effect his murders had on ordinary folk. And, like an unwelcome cousin at a family reunion, it will reawaken memories of those dark nights. How soon will it be before we see the inevitable Ripper movie – a sinister reminder of the harrowing of the North?