Complex sentence: In September 1935, he made his first trip abroad with his parents and his sister Kathleen to London intending to study under Harold Laski at the London School of Economics (LSE) as his older brother had done.
Split into simpler sentences: In September 1935, he made his first trip abroad when he traveled to London with his parents and his sister Kathleen. He intended to study under Harold Laski at the London School of Economics (LSE), as his older brother had done.