Complex sentence: Key was later to reveal, that the sole purpose of this dedicated period of study was to build upon the firm foundation established by his academic training by divesting himself of the influences he had absorbed & so arriving at his own personal artistic language.
Split into simpler sentences: Key was later to reveal, that the sole purpose of this dedicated period of study was to build upon the firm foundation established by his academic training. Divesting himself of the influences he had absorbed & so arriving at his own personal artistic language.