He kept her abreast of what was going on there by leaving secret notes in a confessional in the 16th century San Luigi dei Francesi church, which is famous for Caravaggio paintings that hang on its walls.

She describes the trepidation and fear she felt each time she entered the church to collect the messages, which were hidden inside a ripped cushion. “I got down on my knees, threw a quick look over my shoulder, then inserted two fingers into the material. I felt a piece of paper rustle, and I quickly placed it in the palm of my hand,” she writes. 

On one occasion, a man approached her and asked her if she was alright.  “I breathed a sigh of relief. It was just another churchgoer. It was nobody dangerous… ‘It’s OK, I was just praying,’ I said quietly. The man bowed and went away, but I waited until he left the church before opening the little piece of paper.

“The messages of my friend in the Secretariat of State, left in the confessional to keep me abreast of what was happening in the Vatican, kept me going during those months.” One of the messages she received claimed that the Pope was angry that the trial had gone ahead and wanted it brought to a close as soon as possible.  “This trial has to finish, His Holiness is really irritated,” the note said. 

Another secret communication informed her that her house was about to be searched by Italian police, while a third told her that one of her co-accused, Spanish monsignor Angel Lucio Vallejo Balda, had tried to commit suicide. 

The priest, who had served on the same economic reform commission and was also accused of leaking documents, was held in a cell during the months-long trial, which was held in a Vatican tribunal.  He was also convicted of conspiracy and served around half of an 18-month sentence.  It was then commuted by Pope Francis and he was released. 

The two journalists who wrote books based on the leaked documents were both cleared after the Vatican decided it had no jurisdiction over them. Their books revealed mismanagement, waste and extravagant spending by cardinals, as well as trenchant resistance to Pope Francis’ drive for greater accountability and transparency in the Vatican’s finances.

During the trial, Monsignor Balda claimed that he had been seduced by Ms Chaouqui, breaking his vow of celibacy.  He said they went to bed together in a hotel in Florence, claiming she left a skimpy nightie in his room, but then turned against him, calling him “a worm”.

Ms Chaouqui, who is married, strenuously denied having an affair and insisted that Monsignor Balda was, in any case, gay.  She claims in her book that the Spanish prelate had a gay lover in Rome, for whom he obtained Vatican accreditation as his “butler”. 

Pope Francis has conceded that it was an “error” to appoint Ms Chaouqui and Monsignor Vallejo Balda to the finance commission that he set up shortly after his election in 2013. He suggested that Ms Chaouqui had been driven to leak the documents because of her anger at not being retained by the Vatican once the commission’s work was done. 

The Vatican said it was not concerned by the revelations in the new book. "We're not losing sleep over it,” said Greg Burke, a spokesman.