The Rev. Dr. Alan Patrick Llewelyn Prest, Jr. was born in Detroit, Michigan and grew up in Massachusetts. He earned a degree in business from Lehigh University in 1951 before receiving his Masters of Divinity from the Episcopal Theological Seminary in Cambridge, Massachusetts in 1954. Following his residency in clinical pastoral education at St. Luke's Hospital in Houston, Texas, Prest served a chaplain at Bellevue Hospital in New York City.

After a short tenure at Bellevue, Prest came to the Medical College of Virginia (MCV) where he succeeded the Rev. Dr. George D. Ossman who had served as the first chaplain and as a clinical pastoral educator beginning in 1943. The MCV administration tasked Prest with securing accreditation for the clinical pastoral education program which had been initiated in 1958. Under Prest's leadership the program received accreditation from the Council for Clinical Training (now the Association for Clinical Pastoral Education) one year later. During the pastoral education program's formative years, Prest served as administrator and hospital chaplain. He also established a cooperative program with the School of Theology at Virginia Union University (VUU) for which he was an adjunct instructor teaching courses in pastoral counseling and clinical orientation.