Mark Gilbert works for Certainty4Eternity, an organization established to help churches share the gospel with people from a Roman Catholic background. Mark grew up as a committed Roman Catholic, but despite this did not hear the gospel until he started university. He trained as a doctor before retraining as a minister and has served in Anglican churches in Sydney since 2000. He currently works as an Evangelist on the Northern Beaches of Sydney and partners with churches to help them to reach more Roman Catholics with the gospel. Mark has published a number of books and articles to help including: The God Who Saves, The Road Once Travelled and Stepping Out in Faith. He has also spoken at conferences in Australia, the United States and Europe.

Simon Cowell is originally from Australia but now lives with his family in Italy, the heartland of Roman Catholicism. Simon serves as a university staff worker with the Gruppi Biblici Universitari (GBU)— an evangelical students’ fellowship—and is responsible for the groups in the Puglia region. He trains, mentors and disciples students to share Jesus with their peers. Simon is also involved in the leadership of his local Protestant church.

Chris Overhall is a former primary school teacher who now lives with his family in Santiago, Chile, where most people are Roman Catholics. Chris seeks to train and encourage the next generation of Christian leaders through the Grupo Bíblico Universitario (GBU), a fellowship of evangelical university students. He also teaches Moore Theological College correspondence courses to university students, the GBU Chile leadership team and students in various churches. He serves on the leadership team of his local Anglican church and is involved in one-to-one ministry, Bible study leadership and other general ministry.