Tony Blair has revealed why he overturned government policy going back nearly 90 years to approve the appointment of a Catholic as British ambassador to the Vatican.
The former prime minister tells a BBC Northern Ireland documentary - to be broadcast on Wednesday 17 February - that the policy of banning Catholics from the post was "stupid", "ridiculous" and "discriminatory".
In late 2005 the government appointed Mr Blair's former private secretary, Francis Campbell, as ambassador to the Holy See after the post was advertised.
It was the first time a British ambassador had been recruited from open competition. One hundred and twenty people applied for the job, according to the Foreign Office.
'Yes Minister' moment
In 1917 the Foreign Office issued a memorandum saying that Britain's representative at the Vatican "should not be filled with unreasoning awe of the Pope," and the post had been filled by a non-Catholic until Mr Campbell's appointment.
In the first episode of the three-part documentary series 'Our Man in the Vatican' Mr Blair recalls: "One of the funny things about the Yes Prime Minister show is that if you have actually done the job you realise there is parody but, my goodness, it is parody close to truth.
"And one of the great Sir Humphrey moments was when the ambassadorship to the Holy See became vacant and I said 'Francis would be a great person to do that' and they said 'Well you know this, prime minister, but actually we don't really have this open to Catholics' and I honestly thought I misunderstood what they were saying.
"I said 'How do you mean? We're talking about that Embassy, the Vatican one'. They said 'Yes, I know, but not a Catholic there.'
"I said 'It's the Vatican, the Pope, he's a Catholic. You mean we actually as a matter of policy... say you can't have a Catholic?' I said 'What is this? It's the most ridiculous thing I have ever heard'."
Mr Blair added: "Can you imagine we say for years and years and years the one category of person we shouldn't have as ambassador to the Holy See is someone who shares their faith?
"I don't think that is very sensible - not in this day.
"Quite apart from being discriminatory, how stupid is it? So Francis was the first."
Mr Campbell, a native of Newry, Northern Ireland, is the first Catholic to hold the post of ambassador to the Vatican since the Reformation and was the youngest of nearly 200 British ambassadors when he was appointed at the age of 35.
He will take up a new posting at the end of this year, having played a key role in the planning and organisation of the Pope's historic state visit to England and Scotland in September.
The small team who made the observational documentary was given unprecedented access to a UK ambassador and the Vatican.
The programmes include the first ever filming of a meeting in the Vatican's Secretariat of State and tell the untold story of the surprising level of common interest there is between the Holy See and London, despite their differences over such issues as the Equality Bill currently going through Parliament.