Complex sentence: Fred Willey's political career began in the 1930s as an activist for social justice and other left wing causes: he was the keynote speaker welcoming returning International Brigade volunteers to Sunderland.
Split into simpler sentences: Fred Willey's political career began in the 1930s as an activist for social justice and othe left wing causes. He was the keynote speaker welcoming returning International Brigade volunteers to Sunderland.