Honestly, it sounds like a trick question. If you ask a pub quiz enthusiast how many UK Prime Ministers have been Catholic, they might confidently rattle off a list. But the reality is much weirder, and surprisingly short. For centuries, being a Catholic in 10 Downing Street wasn't just socially awkward—it was essentially a legal impossibility.
We’re talking about a country where, since the Reformation, the state and the Church of England have been tied together like a messy knot. You’ve got a Monarch who is the "Supreme Governor" of the Church of England. So, having a Prime Minister who looks to the Pope in Rome for spiritual guidance? That created a massive constitutional headache that lasted for hundreds of years.
Believe it or not, there has really only been one practicing Catholic Prime Minister while in office. Just one.
The Boris Johnson Bombshell
When Boris Johnson took the keys to Number 10 in 2019, he made history in a way most people totally missed. He was the first person to serve as Prime Minister while being a baptized and practicing Catholic.
Now, his faith journey is—to use a Boris-ism—a bit "topsy-turvy." He was baptized Catholic (his mother’s faith), but then he went off to Eton and was confirmed as an Anglican. For years, he was the classic "nominal" Church of England guy. But then 2021 happened. He married Carrie Symonds in a secret ceremony at Westminster Cathedral.
The Catholic Church is pretty strict about marriage. To get married in the Cathedral, the Church had to recognize him as a Catholic. That wedding effectively signaled that Boris had "come home" to his original faith.
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It was a huge deal. Why? Because the PM has to advise the King on who to appoint as Bishops in the Church of England. There’s actually an old law—the Roman Catholic Relief Act of 1829—that says a Catholic PM can’t technically do that. When Boris was in charge, he basically had to step back from those specific churchy duties and let another minister handle them.
What About Tony Blair?
This is where everyone gets confused. You’ve probably seen the photos of Tony Blair meeting the Pope or heard about his deep faith. He spent ten years as Prime Minister (1997–2007) regularly attending Mass with his wife, Cherie, and their kids.
But here’s the kicker: Tony Blair was not Catholic while he was Prime Minister.
He was an Anglican. He waited until after he left office—literally months after moving out of Downing Street—to officially convert and be received into the Catholic Church. His spin doctor, Alastair Campbell, famously once said, "We don't do God." Blair knew that converting while in power would have triggered a media firestorm and a constitutional crisis.
He basically spent a decade "waiting in the porch" of the Church. He felt at home there, but he couldn't officially join because of the job.
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The Long Shadow of the 1829 Act
To understand why this list is so short, you have to look at the law. For a long time, Catholics were banned from public life entirely. They couldn't vote, they couldn't sit in Parliament, and they definitely couldn't lead the country.
The Catholic Relief Act of 1829 changed a lot, but it kept some weird "poison pill" clauses. Even today, if a Catholic is PM:
- They cannot advise the Monarch on Church of England appointments.
- They are technically barred from holding certain ancient offices (though most of this has been smoothed over by modern law).
- The "Statutory Bar" remains a strange relic of the 1600s.
It’s kind of wild that in 2026, we still have these hangups. We’ve had a Hindu Prime Minister in Rishi Sunak. We’ve had atheists. We’ve had plenty of Anglicans. But the "Catholic question" still feels like the final frontier of British political religion.
Why It Still Matters
People sometimes think religion in politics is dead in the UK. We aren't like the US; we don't expect our leaders to preach from the podium. But the "Catholic Prime Minister" tag still carries weight because of Ireland, the history of the Union, and the unique way the UK government is still tethered to a state church.
When Keir Starmer took over, the conversation shifted again. He’s described himself as not being a person of faith, though he respects it. This makes the "practicing Catholic" count even more exclusive.
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If you’re looking for a definitive list of UK Prime Minister that were Catholic while in power, the list is:
- Boris Johnson (The first and, so far, only one).
If you count those who converted after their term:
- Tony Blair.
That’s it. In over 300 years of the office existing, that is the entire roster.
Actionable Insights for History Buffs
If you're digging into this for research or just general interest, here are a few things to keep in mind:
- Check the timing: Always verify if the PM was Catholic during their term or after. Most "lists" online get this wrong.
- The 1829 Act is key: If you want to understand the "why," read up on the Roman Catholic Relief Act. It explains the legal barriers that stayed in place long after people stopped caring about the theology.
- Watch the "Established Church" debates: As long as the Church of England is the state religion, a Catholic PM will always have a slightly different legal experience than a Protestant one.
The reality is that Britain is a lot more secular now, but its bones are still very much built on the old Protestant-Catholic divide. Boris Johnson breaking that seal was a bigger historical moment than his critics (or fans) usually give it credit for.
To get a better handle on how this affects current politics, you should look into the "Lord Chancellor" role, which has similar historical baggage regarding Catholicism. It's a rabbit hole, but a fascinating one.