In January 1959, Pope John XXIII announced a council of all the world's Catholic bishops and cardinals in Rome.
It led to sweeping reforms, including allowing Mass to be said in languages other than Latin and an attempt to build relationships with other denominations and faiths.
But not everyone was happy with the changes.
Monsignor John Strynkowski was a student priest in Rome at the time and told Rebecca Kesby about the excitement and controversy surrounding the council that became known as Vatican II.
This programme was first broadcast in 2019.
(Photo: Pope John XXIII. Credit: Getty Images)