Complex sentence: He was educated at Winchester College, then as now noted as among the most intellectually rigorous of English public schools, and then spent some time with a firm of accountants, before joining his father as an assistant in 1894.
Split into simpler sentences: He was educated at Winchester College, noted as among the most intellectually rigorous of English public schools. He then spent some time with a firm of accountants before joining his father as an assistant in 1894.