He’s been at the pope’s side, walking slightly behind him, whispering in his ear, everywhere Francis has gone on this US trip, from his speech at the White House to a lunch for the homeless at Catholic Charities.

Pope Francis’ shadow is also his translator: Monsignor Mark Miles, a dimpled 48-year-old official of the Vatican’s Secretariat of State who, despite his efforts to keep a low profile, has tons of fans in the blogosphere and on social media.

Originally from Gibraltar, Miles has a job many would both covet and fear: translating for the pope. Miles’ native language is a heavily accented British English. Spanish is his second language.

History’s first pope from the global south has said many times he’s not comfortable speaking in a language other than Spanish or Italian. So he usually taps Miles to transmit his message to English speakers: from peons to presidents, they all hear the pope through him.

It also means that Miles has to be ready when Francis ditches his prepared speech to have “conversations,” as he likes to say. The pope is famous for doing this, particularly when talking to religious communities, the youth, or the poor.

Miles was first faced with the challenge of relaying one of Francis’ improvised messages to a huge crowd when Francis visited the Philippines in January. The pope was celebrating a Mass at the typhoon-destroyed city of Tacloban, to try to comfort the families of the more than 6,300 people killed by Typhoon Yolanda in 2014.

Rushing because of another typhoon alert, the pope decided his prepared homily didn’t quite capture what he wanted to share, so he asked the crowd if he could wing it.

“I have a translator, a good translator,” he said. “May I do that? May I?” The crowd roared its approval, and Francis delivered one of the most touching addresses of that trip, with Miles translating word for word. Well, almost: The pope speaks an Argentinian dialect, so he sometimes uses terms only a fellow countryman could understand. On that occasion, it was the word “skirt:” pollera for Argentines, falda for the rest of the Spanish-speaking world.

Of the 18 addresses, speeches, and homilies Francis will deliver during his six-day visit to Washington, New York and Philadelphia, only four will be in English. The rest will be in Spanish. And odds are, sooner or later he’ll go off-script, and that’s when Miles’ hardest job will begin.