Complex sentence: Glanville maintained an interest in a large number of institutions and served on many of their councils, in November 1950 he was elected to the office of President of the Institution of Civil Engineers and was the youngest person to have held that office up to that time.
Split into simpler sentences: Glanville maintained an interest in a large number of institutions and served on many of their councils. In November 1950 he was elected to the office of President of the Institution of Civil Engineers and was the youngest person to have held that office up to that time.