What's the name of the stunning aria sung at the Princess of Wales's funeral, and subsequently used in the funeral scenes of the 2006 movie 'The Queen'?

The conclusive piece, Giuseppe Verdi’s “Libera Me” from his 1868 work the Manzoni Requiem, is the actual operatic aria which was performed at Diana’s funeral at Westminster Abbey in London, by Lynne Dawson and the BBC Singers. It is, quite rightly, stately, and regal, and hugely emotional, but the live recording doesn’t really do the piece justice, and while its inclusion is certainly musically representative of the film, it somehow feels “tacked on”, and not at all fitting with the rest of the score.

https://www.awesomestories.com/asset/view/Verdi-Lynne-Dawson-Sings-at-Princess-Diana-s-Funeral