The National Youth Choir of Great Britain have released a filmed live performance of Messiaen's a cappella choral work O Sacrum Convivium, conducted by Stephen Layton. It's a captivating and superbly-controlled account:

If you feel inspired to listen to further recordings of this work, you could try 'Refractions', an album by the Norwegian Soloists Choir conducted by Grete Pedersen on BIS, which also includes music by Berg, Webern and Valen (read the review here). Alternatively, there is the Choir of Trinity College, Cambridge and conductor Richard Marlow on Conifer, who paired the Messiaen with Fauré's Requiem and Cantique de Jean Racine (reviewed in Gramophone's October 1990 issue).