Complex sentence: He became Lord of Trade in December 1759 and zealously applied himself to its work, remaining in office until 1765 with an attendance at Board meetings during that time of nearly 80 per cent.
Split into simpler sentences: He became Lord of Trade in December 1759 and zealously applied himself to its work. He remained in office until 1765 and his attendance at Board meetings during that time averaged nearly 80 per cent.