In 1921–22, he became engaged to Kitty Kiernan. Under Kiernan's influence, he would resume Catholic religious practice (though retaining secularism as a political position), despite his previous hostility to the Irish Catholic hierarchy. He made a general confession before his departure for London to negotiate the Anglo-Irish Treaty. While in London, his practice of lighting votive candles for Kiernan developed a habit of attending mass daily, usually at the Brompton Oratory. In letters between the two, he credits Kiernan as having given him a newfound appreciation of Confession and Communion. Collins attended mass regularly throughout the ensuing civil war.