It was already the most chilling show in town — what with the half-hints of ghastly child corruption in Henry James’s masterly ghost story, the brilliantly sinister music conjured up by Benjamin Britten with 13 instruments and six voices and a David McVicar staging that suggests layer upon layer of intangible evil without imposing any fixed view of who is inflicting what horror on whom.

But English National Opera’s revival of McVicar’s 2007 production turns the screw even tighter. You still feel queasily uncertain about whether the governess, intent on saving the two children in her care from psychological, moral and perhaps sexual danger, is herself the chief source of it. Or whether the predatory servant Peter Quint and his creepy lover Miss Jessel are “only” ghosts, or figments of the governess’s overwrought imagination. And you are still unsettled by the hatchet-faced Victorian servants flitting round Tanya McCallin’s eerily translucent sets, and by the dead leaves on the floor. It’s as if the whole drama is an exhumation of distressed souls haunting a long-abandoned mansion.

But McVicar seems to have rethought and considerably strengthened how the children are played by the excellent Charlie Manton and Nazan Fikret. Their sadistic nursery games have been toned down and the boy Miles’s flirtation with the governess made less explicit. So the question of whether they have been possessed — as the outstanding Rebecca Evans’s sexually frustrated, neurotic governess chooses to believe — is left even more open.

That’s one change. Another is the truly demonic Quint created by the one adult newcomer to the cast, Michael Colvin. He’s almost bestial with his claw-like hands, hunched back, lurching gait and spookily disembodied singing. With Ann Murray returning as the morally compromised housekeeper and Cheryl Barker repeating her mad-eyed Miss Jessel, one can’t imagine the dark, depraved depths of this story being more effectively probed.

And on top of all that is Sir Charles Mackerras. Astonishingly, 53 years have passed since he last conducted this opera in London. But any fears that the veteran Aussie, 84 next month, would amble through the score are dispelled by the first, insidiously unsettling orchestral chord. Mackerras paces the drama with tremendous tautness, but also conjures up a series of arresting instrumental timbres that add an aural dimension of dread to an already terrifying tale. One effect — the icy, slowly spreading string harmonics as details of Quint’s death are revealed — will haunt my nightmares for weeks.

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