Complex sentence: Like many of his contemporaries he left the Teify Valley to work in the city as a deliverer of milk and he became highly successful, and the first holder of London Retail Dairymen's Association.
Split into simpler sentences: Like many of his contemporaries he left the Teifi Valley to work in the city as a deliverer of milk. His business was very successful, and he became the first leader of the London Retail Dairymen's Association.