LONDON — One week ago, the funeral of Queen Elizabeth II attracted a huge global audience. An estimated 4 billion people across the world watched or listened to the state funeral of the British head of state.

One of the solemn moments of the ceremony involved a piece of music specifically composed to reflect the late monarch’s Christian faith. Entitled: Who Shall Separate Us?, the anthem was inspired by Chapter 8 of St. Paul’s Letter to the Romans. Its composer is the Scottish Catholic composer Sir James MacMillan.

Born in Scotland in 1959, MacMillan grew up in what he describes as “a strong Catholic community in the west of Scotland, where there were important links between families, schools and parishes.” But even then, it was music, he says, that provided his spiritual direction, even from an early age. “I was co-opted to help with music and liturgy at school and in the parish,” he recalled. “Being close to the organization of worship, and being involved in the ritual prayer of the Church, and being regularly in the vicinity of the Blessed Sacrament were all sustaining experiences and influences on my life. Then, when I went to the University of Edinburgh, I came into close contact with the Dominicans, and that helped me grow from a childhood Catholicism to something that would shape my adult life.”

Today, Sir James is among the top-five most-performed living classical music composers in the world; his music is regularly heard on classical music stations in the United Kingdom and beyond. Although his compositions are very much part of modernism in contemporary classical music, he is an outspoken defender of the value of tradition in art. Intriguingly, in the radically secular world of modern classical music, he is also a devout Catholic.

Reflecting on this historic occasion, and his part in it, Sir James spoke to the Register via email a few days after the funeral.

When were you approached to compose for the funeral of Queen Elizabeth?

The first discussions about this took place in 2011. As most people realize, these things take years to plan ahead. Just look at how the BBC and other broadcasters had material from years back, ready to roll during the mourning period. And Simon Armitage didn’t write his laureate poem in the days after the Queen’s death. Like Judith Weir and I, he was likely asked to deliver years in advance.

How did you feel about being asked to compose for such a momentous occasion?

I was deeply honored to have been invited to write this anthem.

What freedom were you accorded in composing it?

The text was suggested, as it had significant resonances with Her Majesty. I was happy to set this particular passage from Romans, Chapter 8.

What inspired you in that biblical passage: “Who shall separate us from the love of Christ?”

It is a text which reflects Queen Elizabeth’s relationship with Jesus and provokes the rest of us to look deeply at what it means to have an ongoing search for Christ.

How did you feel when you heard this piece performed to a global audience?

Astonished! I was told that there was an international audience of between 4 and 5 billion people. I can’t really take that in.

What reaction has there been? Do the royals comment in such circumstances?

I’ve tried to avoid engaging with a tsunami of reaction. The royals don’t comment.

A Catholic composer at an Anglican court has historical precedent, but did this inhibit in any way in your composing for the monarch’s funeral?

No. I have no issues with Anglicans! They have been amongst my most fervent friends and supporters all through my life in music. And, to be honest, Catholics in the U.K. are among the most ardent supporters of our constitutional monarchy, especially with Elizabeth, as she has been the most effective and persuasive defender of religious ideas in the public square in recent years. And in that sense, Catholics have always felt her as a protector of Christian values in an increasingly hostile political and social environment.

There have been some political points made about your composition, with Scottish nationalists suggesting that it had a “Unionist” agenda. How would you respond to this?

It’s not just Scottish nationalists who are ignorant of Scripture, but it was especially amusing to see some of them imagining that the title of my anthem Who Shall Separate Us? had any connection with Scottish-British politics. St. Paul, in his Letter to the Romans, didn’t have much to say about Scottish constitutional rearrangements …

What are you working on next?

My labor of love: “The Cumnock Tryst,” an annual music festival in East Ayrshire, Scotland, which begins again on Thursday, Sept. 29. I would love to welcome all-comers to the bonny, Burnsian East Ayrshire town any time in the autumns ahead.