According to the Installation Blog for Archbishop Vincent Nichols, "Composer James MacMillan has been commissioned to write three enthronment antiphons for the Mass of Installation and Colin Mawby a trumpet fanfare. We hope to provide more information about this in the next day or so."

I don't have a fully-formed opinion yet of his music; you can hear some samples below. (I didn't really like any of them.) Has he composed any polyphony?

(source)

BBC Philharmonic - James MacMillan
James MacMillan
Intermusica / Artists / James MacMillan / Biography
Composer James MacMillan warns of liberal elite's 'ignorance-fueled hostility to religion'


YouTube - dePreview 29 november interview James MacMillan


'Kiss on Wood' by James MacMillan


VU-Kamerkoor: MacMillan - Te Deum (part 1 of 2)
VU-Kamerkoor: MacMillan - Te Deum (part 2 of 2)

Veni Veni Emmanuel: II. Heartbeats
Veni Veni Emmanuel: III. Dance - Hocket
Veni Veni Emmanuel: V. Gaude Gaude
Veni Veni Emmanuel: VII. & VIII. Dance - Chorale & Easter