Thus Mellors mirrors the novel’s function, since in talking sex to Connie he helps effect a similar integration in her. But her accompanying practical lessons are not, it turns out, necessary. It is sufficient to learn by overhearing Mellors and Connie’s consciousness when love-making: “Today, the full conscious realisation of sex is even more important than the act itself. After centuries of obfuscation, the mind demands to know and know fully.”

Of course, for Lawrence to “know” sex “fully” did not mean to know it as Don Juan, Swinburne or Freud knew it, but to have “a proper reverence for it”. In his essay “Pornography and Obscenity”, written at the same time as “A Propos”, he argues that what is considered obscene not only varies between cultures and over time, but between the judgment of what he calls the “mob self” and the “individual self”. The former, which is allied to public opinion, is defined by Lawrence as itself obscene, because it has turned sex into a dirty secret. The innocent understanding of sex which characterised Chaucer was lost in the Renaissance, since when European art has either denied its existence (as in the art of Gainsborough), or treated it as a forbidden fruit (as in Jane Eyre). To do the latter is, to Lawrence, pornographic: “Pornography is the attempt to insult sex, to do dirt on it. This is unpardonable.” It is also far more likely to incite masturbation than the “moderate rousing of our sex” which is produced by, for example, Botticelli’s Venus. Hence “Boccaccio at his hottest seems to me less pornographical than Pamela . . . or a host of modern books or films which pass uncensored” — or vulgar seaside postcards or smoking-room anecdotes: “ugly and cheap they make the human nudity, ugly and degraded they make the sexual act, trivial and cheap and nasty.”

There have of course been many literary and film representations of sex as not degraded since Lady Chatterley’s Lover, and many of these are in the novel’s debt. But Lawrence was less interested in blazing a trail in art than in souls. And the latter work is, to put it mildly, unfinished — at least, if not especially, in Anglo-Saxon countries. Certainly Lawrence considered England to be peculiarly pornographic: “I am sure no other civilisation, not even the Roman, has showed such a vast proportion of ignominious and degraded nudity, and ugly, squalid, dirty sex. Because no other civilisation has driven sex into the underworld, and nudity to the W.C.” Even the young bohemians, kicking against their parents’ “eunuch century”, “have the grey disease of sex-hatred, coupled with the yellow disease of dirt-lust.” Waxing (as Lawrence tends to) physiological, he explains that the sex and excretive functions are opposite “in direction” despite being proximate — tending respectively towards creation and disintegration. In healthy people the distinction between these is sharp; in degraded people it is obliterated, and “sexual excitement becomes a playing with dirt”. It is obvious how strong this connection remains, especially in what is today called pornography.

Lawrence’s attempted solution is a frankness which will dispel the masturbatory “dirty little secret”. The giggling media reactions to such sex as there is in the latest adaptation confirm that the representation of sex is almost invariably treated as the “rubbing of the dirty little secret”. The “mild little words that rhyme with spit or farce” (or punt or cluck) remain restricted by BBC decency guidelines which Mercurio chose not to push. Lawrence wanted us to be “able to use the so-called obscene words, because these are a natural part of the mind’s consciousness of the body” — and I am sure that many a modern couple refers lovingly to “fucking” and the “cunt”.