Plan of Prayer for Union
The League's founders understood from the outset that advocating unity between Christians must essentially be a spiritual endeavour. In 1845, Fr Ignatius Spencer CP, Edward Pusey and the future Cardinal Newman won a measure of official approval for a scheme of parallel prayer for unity between Anglicans and Catholics, based on a similar scheme of Spencer's in France and Germany.

Ascension Day, Pentecost and the Ascensiontide Novena
In the 1880s and 1890s, amid high hopes among Anglican leaders for reunion, both the Lambeth Conferences and Pope Leo XIII designated days of prayer between Ascension Day and Pentecost. Although these hopes were disappointed, authorities on both sides agreed to disagree and re-affirmed their commitment to continue in the prayers for unity they had already authorised. The second Lambeth Conference in 1878 had designated Ascension Day as a day of prayer for unity. In 1894, the Catholic-spirited Methodist layman, Sir Henry Lunn, promoted 'Home Reunion Conferences' at Grindelwald in Switzerland, proposing Whitsunday (Pentecost) as a day of prayer for Unity between the great Christian traditions. This was warmly taken up by Archbishop Edward Benson of Canterbury in 1894 and 1895. And then in 1896 Leo set aside Ascension Day to Pentecost as a Novena of Prayer for Christian Unity on a permanent basis. Ascensiontide and Pentecost remain as popular and official times of prayer for Unity. Especially in the Southern Hemisphere, this is the alternative period used for observing the Week of Prayer for Christian Unity itself.

The Church Unity Octave
In the next decade, in 1908 the Revd Spencer Jones, vicar of Moreton-in-the-Marsh, and Fr Paul Wattson, founder of the Friars of the Atonement in New York State, jointly founded the Church Unity Octave, to foster deeper desire for unity, especially through a reunited Church reconciled through the Catholic faith and communion with the Bishop of Rome. The Octave was sanctioned by Pope Pius X at the same time as it grew in Anglican circles, indicating that people in both churches understood how urgent unity and an end to separation were.

So, from its foundation in 1913, the Catholic League promoted the Church Unity Octave with prayer for the recovery of visible, corporate communion among Christians. Its intention was to rediscover the true identity of the Catholic Faith for a modern age, in fellowship with the successor to St Peter and St Paul in Rome, together with all his Catholic brothers and sisters, throughout the world and not least in England.

The Malines Conversations and the Monks of Unity - Mercier and Beauduin
The Malines Conversations, facilitated by Cardinal Mercier of Brussels, were an early fruit. Although the English Catholic bishops at the time were ill disposed to them, the authorities in Rome understood that England's religious landscape was unlike that in other post-Reformation countries and that something could be gained by fostering contacts between Anglicans from England and continental Catholics. Founding members of the League were involved in the Conversations from the Anglican side, both in preparations in London and in the sessions themselves from 1921 to 1925. In the aftermath of the 'total' World War I, a good deal of it fought out across Belgium, both Cardinal Mercier of Malines-Bruxelles and Viscount Halifax as leader of the Anglican delegation saw the need for the reunion of Christendom as important spiritually as the recent political foundation of the League of Nations was seen to be in the cause of world peace. A decisive part in the Conversations was played by Dom Lambert Beauduin, a leading figure in the Liturgical Renewal movement, whose foundation of the Monks of Unity Mercier had encouraged at Amay-sur-Meuse. Beauduin was asked to write a paper to answer a question from the Anglican side about how a new space within the Catholic Church could be created for Anglicans, if it were the case that Catholic structures and formularies could not be adapted to accommodate those of Anglicans. Beauduin echoed Johann Adam Möhler's theory of 'unity in diversity' in a stimulating or even provocative thought-piece, suggesting 'The Anglican Church United, not Absorbed'. The Conversations were a landmark in Anglican-Catholic relations and are widely seen as the forerunner of the modern Anglican-Roman Catholic International Commission.

Paul Couturier - Spiritual Ecumenism and the Week of Prayer
Beauduin's community later moved to Chevetogne, where its ecumenical work continues to this day. But it was at Amay that Paul Couturier went on retreat and began his own apostolate of spiritual ecumenism, effectively re-founding the Church Unity Octave as the modern Week of Prayer for Christian Unity from 1933 onwards. The main work of the Monks of Unity was the rapprochement of the Latin and Orthodox traditions - it is a joint community of two groups of monks using the Latin and the Byzantine rites respectively. But, thanks to Beauduin's appreciation of English Christianity, Couturier came to learn much about Anglicans and the importance of reconciliation especially in England.

It was the leaders of the League who therefore invited him to come and see Christianity in England at first hand. Ever since, the League and its members have actively promoted his teaching on ecumenical prayer and the Week of Prayer itself. His influence and principles were later brought to bear on Vatican II, where his thoughts on spiritual ecumenism were enshrined in the Decree on Ecumenism. Recently, Cardinal Kasper, president of the Pontifical Council for Promoting Christian Unity, has issued a Handbook on Spiritual Ecumenism to encourage all Catholics alongside other Christians to remember that Unity in the Church is integral to the discipleship of the Christian : if we are to achieve spiritual union with him in the life of the Spirit, it will be a voyage of discovery as we come closer to each other as we converging upon him. The Catholic League is particularly proud that it has commended this spiritual pathway to unity throughout its life and witness.

Catholic Spirituality of Ecumenism
Although never numerous, the members of the League have resolutely maintained the need for a Catholicism which is ecumenical and an ecumenism that is Catholic - for the benefit and development of the whole Christian Church, if it is to transcend its earthly separations and become a more effective realisation in this world of the Kingdom of God to come, on earth as it is in heaven. The original Anglican founders understood, as Cardinal Newman had done, the benefits of reform and development in the life and progress of the Church. They recognised the increasingly prevalent idea of corporate unity in individual and local diversity. They accepted the cultural, political and spiritual unrealism of expecting the various Christian churches to become mere copies of Roman Catholicism, however much they themselves embraced liturgical and devotional practices from contemporary Catholicism to enrich the vitality and mission of their own Church.

Proclaiming the Gospel of Jesus was paramount, and without unity this cause suffered harm and even discredit. The founders of the Catholic League were among the first to maintain not only that reconciliation among Christians was desirable out of obedience to the prayer of Christ himself, but also that there can be no authentic and lasting unity unless it takes seriously the Catholic Faith, as it is now, and the need to 're-compose' the visible integrity of the Church, through the reconciliation of all Christians with the see of Peter, and importantly vice versa. Essentially this is a work of unceasing and urgent prayer. It is marked with penitence for the sins and cruelties of the past and Christianity's continuation of its separations. But it is also marked with prayer for closer conversion to Christ and union with him in the Holy Spirit. It is in this convergence upon him, that the prayer of Christ on the night before he died is answered in the unity of his followes in faith and service to the world:
Father, may they all be one in us, as you are in me and I in you, so that the world may believe it was you who sent me.
The foremost work of the Catholic League is therefore its daily prayer for the unity that Christ wills. All its members take part in its Apostleship of Prayer, devoting especially this prayer for peace at every Eucharist for the unity of Christians:
Lord Jesus Christ, who said to your Apostles,
Peace I leave you, my peace I give you:
look not on our sins,
but on the faith of your Church,
and be pleased to grant her peace and unity
in accordance with your will,
Who live and reign for ever and ever.