The revelation that Channel 4 has made a drama-documentary imagining the kidnapping of Prince Harry by the Taliban has brought immediate criticism. The detractors regard this commission as typical of a lefty, subversive, trouble-making channel, which has previously aired similar fantasy dramas depicting the murder of President George Bush and Gary Glitter's execution for paedophilia.

Yet, strangely, the godfather of this genre of snuff hypotheticals is one of the most popular and populist writers in Britain, who once served as a deputy chairman of the Conservative party. In 1977, Jeffrey Archer published his second novel, Shall We Tell the President?, in which FBI agents attempt to prevent a plot to take the life of President Edward Kennedy. To place the youngest of the Kennedy brothers in the White House was fiction, but since the politician's two brothers had been assassinated, the book was widely viewed as being in dubious taste.

Archer was following a tradition in mainstream fiction of speculative violence against historical figures. Geoffrey Household's Rogue Male (1939) featured a plot to kill Hitler, Jack Higgins's The Eagle has Landed (1975) turns on an attempt to kidnap Winston Churchill, and the protagonist of Frederick Forsyth's The Day of the Jackal (1971) is trying to shoot General De Gaulle, but the politicians in question were either already dead or (in the case of Rogue Male) despised when the stories appeared. The risky innovation of Shall We Tell the President? was to use someone who was both living and liked by many. The sister-in-law of Archer's imagined target, Jackie Onassis, then working in the New York book world, campaigned against publication and Archer rewrote the novel with an invented president.

The arguments exchanged at the time of Archer's book are exactly those that apply to Channel 4's trilogy of what-if killings: Death of a President, The Execution of Gary Glitter and, now, The Taking of Harry. The justification for such projects is that one of the functions of fiction is to examine the dreams and fears of a society. In the 70s, it was a common dread among Democrats that they would get a second President Kennedy and then lose him. This was openly spoken about and so logically can be openly written about. Unfortunately, Archer did not dramatise this shadow on the American psyche with any depth or complexity.

The Channel 4 dramas are more defensible in that, at their best, they force viewers to examine their beliefs and prejudices. Demographics suggest that the majority of the network's audience would be instinctively anti-Bush, opposed to capital punishment and sceptical about the monarchy. In this context, these dramas say, in effect: be careful what you wish for. An anti-Iraq protester who might metaphorically have wished Dubya dead – or felt indifferent to the fate of Prince Harry – is forced to confront the darkness of these thoughts. Liberals who believe all criminals should live are asked whether they might make an exception for an old man who rapes young girls.

The main argument against such projects is taste. There is a general social superstition against speculating about someone's death: for this reason, the media proceed with great care and tact in making pre-recorded obituaries of celebrities.

There is a substantial moral difference between a programme that imagines Bush or Blair or Benedict XVI on trial – a consoling fantasy for their detractors of something that in reality will never happen – and a fiction depicting a tragedy that is a plausible risk. One of the reasons Death of a President seemed so questionable was that real footage was redeployed with what might be taken as gloating coldness: news clips of the first lady and Dick Cheney in dark clothes at the funerals of Presidents Reagan and Ford was presented as their attendance at the state obsequies of Bush.

If it follows the models of its predecessors, The Taking of Harry may work intermittently as drama but, as has been shown, it operates impeccably as publicity. Which is why Channel 4 will continue down this line.