Actor Steve Coogan and Philomena Lee, whose story inspired the Oscar-nominated film Philomena, have met Pope Francis in Rome.
Coogan, who starred in, co-wrote and co-produced the film, will take part in a press conference with Ms Lee in the Italian capital on Thursday.
They are campaigning for the release of 60,000 adoption files held by the Irish state, churches and private agencies.
The film tells the story of Ms Lee's search for her adopted son.
As an unmarried mother in Ireland in the 1950s, Ms Lee was put into a convent as a "fallen woman" and forced to give up her three-year-old son.
Coogan, who describes himself as a "lapsed Catholic", told BBC Radio Manchester the pontiff "gave the meeting his blessing beforehand".
"I spoke to him and introduced him to Philomena and he listened attentively," he said. "It was quite moving really."
"The invitation came from the Vatican when they became aware of the project as a way of reaching out and giving a significant signal."
Ms Lee said in a statement: "I am honoured and delighted to have been in the presence of Pope Francis.
"As the film portrays, I have always put great faith in the church and the good will to put the wrongs of the past right.
"I hope and believe that his Holiness Pope Francis joins me in the fight to help the thousands of mothers and children who need closure on their own stories."
Ms Lee and her daughter Jane recently launched The Philomena Project to help reunite families separated by adoption.
At present, adopted children who are trying to find their biological parents in Ireland are not permitted to see documents containing information on the identities of parents and children.
Adoption was sometimes forced upon single mothers due to the stigma of having a child outside marriage.
Ms Lee's story was told in a book by former BBC journalist Martin Sixsmith, and his book was adapted for the screen by Coogan.
The film has four Oscar nominations, including best picture, best actress for Dame Judi and best adapted screenplay for Coogan and co-writer Jeff Pope.