Complex sentence: Since its rapid growth in the 19th Century there have been a series of influxes of immigrants, notably Irish (19th Century), Poles (1940s-50s) and people from South Asia.
Split into simpler sentences: Since its rapid growth in the 19th Century there have been a series of influxes of immigrants. Notably Irish (19th Century), Poles (1940s-50s) and people from South Asia.