Messiaen applied a star rating system to his own compositions: one star meant “characteristic” of his style, two meant “very characteristic”. He gave none to L’Ascension (1932-3), an early spiritual work written originally for orchestra and later revised for solo organ.

To anyone else, this half-hour piece, drawing on chorale and plainchant all wrapped up in tone-clusters of intense, mystical colour, seems quintessential of the French master, the centenary of whose birth is celebrated this year. It featured in the Ascension Day Eucharist service at Westminster Abbey — standing room only — interspersed with Poulenc’s ethereal Mass in G, sung by the Abbey choir, directed by James O’Donnell. Usually we hear Messiaen’s major works only in the concert hall (L’Ascension is also being played at the Proms). Yet his single dominant feature is his Christian belief as expressed through music. Experienced in the context for which it was intended, the music’s static, and ecstatic, qualities make perfect sense.

Organist Robert Quinney conjured exquisite variety from the Abbey’s Harrison and Harrison organ, refurbished two years ago and now boasting five manuals and 109 stops.

The congregation was a mix of those who had come for the service, those for the music, with a few non-believers on either side. French Catholic stained glass exoticisms do not necessarily chime with the Anglican soul. Messiaen was robust towards those who complained about his “so-called” dissonances: “I say to them quite simply, I am not dissonant; they should wash their ears out.” Quite so.

Southbank Messiaen Festival continues 10.30am, 11 May, Pentecost Mass, Westminster Cathedral.