Hillier was born in Kent to Anthony and Susan Hillier as the eldest of three boys. He studied English literature at King's College and then went on to train at RADA from where he went straight into the prestigious BBC production of Great Expectations.
Hillier was born into a family in Kent, being the oldest of three brothers. He pursued a degree in English literature at King's College before enrolling in RADA, where he swiftly joined the esteemed BBC's adaptation of Great Expectations.