It means virgin birth, don’t you know. Premiered in 2000, this relentlessly profound take on the Annunciation from James Macmillan with words by poet Michael Symmons Roberts now gets a Katie Mitchell production. Musically, it’s great but you can’t call it drama.

It’s based around a modern case of parthewotsit when a German mother’s near scrape with a bomb apparently made her fertilise herself. Roberts gives us the progeny, Anna, dying slowly in hospital 24 years later, imagining an angelic visit that might have proclaimed her birth.
The piece feels like an oratorio, with Anna’s portentous ramblings acting as recitative between sung episodes from Angel (Stephan Loges) and mother Kristel (Amy Freston). Macmillan’s music, provided by the Britten Sinfonia under the composer’s own baton, is all chaos intermingled with grace.

Shivering textures and drums that barrack away like panic or bombs give way to moments of serenity.

The Angel, in particular, is a confused figure — his graceful, noticeably consonant theme persistently undermined.

The standout section of the night is Freston’s second aria ­— a thrillingly sung, stutteringly set text that mixes libidinous frustration and terror.

What the words were, though, I barely guessed: opera vowels. The action doesn’t help — Vicki Mortimer’s set splits the two protagonists: they face us while theoretically responding to each other with unfathomable gestures.

Roberts provides a guide to how deep it all is in the programme. It’s clear that this is a piece where things are touched and ruminated upon rather than, well, happen. It should find its place in the concert hall.

Until 18 June. www.roh.org.uk.