Complex sentence: He first trained with his father, but showed an inclination for drawing by producing some small pencil portraits, principally of family members and so he was entered in the Royal Academy Schools in London in 1786 at the late age of about 25.
Split into simpler sentences: He first trained with his father, but showed an inclination for drawing by producing some small pencil portraits, principally of family members. He was enrolled in the Royal Academy Schools in London in 1786 at the late age of about 25.