For when she was christened in 1954, the parish priest – despite being a cousin of her devout RC paternal grandmother – refused to allow the monicker because it was not a saint’s name.

He pointed out that there were 7,000 saints to choose from but no saint Cherie.

As the former PM’s wife reveals in a previously unremarked passage in her controversial memoirs Speaking For Myself : “A compromise was eventually reached and I was baptised Theresa Cara: Theresa being a bona fide saint and Cara being Latin for Cherie.”

The mother of four – whose ex-Anglican husband Tony converted to Catholicism last year – even kept a bank account at her local Liverpool branch of Lloyds TSB in the name of TC Booth until 1997.

The rather exotic-sounding name Cherie had been chosen by her actor parents Tony Booth and Gale Howard after a young Welsh girl they had befriended while in a repertory theatre.

A friend insists Cherie’s dual name is nothing unusual among devout Catholics: “Her name has always been Cherie. It’s just Catholic tradition to be named after a saint when you’re baptised.”

A spokesperson for Cherie declined to comment. But her religious credentials have not – as reported – led to her hanging a life-size picture of Pope Benedict XVI in her Connaught Square, London, home.

Speaking to a reporter visiting the house from a Catholic newspaper, she insists: “You’re welcome to have a good search but you won’t find it!”