Welcome to the inquiry on the BBC World Service with me Ruth Alexander. Each week we bring you four expert witnesses answering one pressing question from the news.

On August the 11th this year the Pope received an unusual delivery.

A Pope hasn't received something like this, apparently, since the 1300s.

Most Holy Father, the Father, the letter began in Latin.

With profound grief, it read, we are compelled to address a correction to your holiness on account of the propagation of heresies.

The 25-page letter accused the Pope of allowing the spread of uncatholic views, a staggering allegation to make to the person who has supreme

authority in the church.

The letter was signed by 62 theologians and priests and was also posted online

where it's gathered more signatures becoming effectively an online petition.

With such a public questioning of the Pope's commitment to the faith he

leads, we're asking, is the Pope Catholic?

Part 1. Doubts and Corrections.

It's about the size of an 18-hole golf course, the actual Vatican City State.

The Vatican is where our first expert witness, Christopher Lamb, spends much of his time as Rome correspondent

for the Catholic news magazine The Tablet. Vatican City is the smallest independent state

in the world, and it's where you'll find the headquarters of the Roman

Catholic Church. That's all housed in Renaissance glory, Renaissance palaces so you

go into meet people there and you walk past the first maps painted by Dante and it's like you feel the sense of history and it's kind of overwhelming.

But then you have a more modern part of the Vatican City State, which is where Pope Francis lives in this residence, the Khazas and Amata, and that's like a three-star hotel kind of place.

The Pope lives there in just two rooms.

He could have a grand apartment on the top floor of a palace.

Popes normally do.

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