Complex sentence: Chamberlain began to make a case that actual Allied losses had been light and German losses disproportionate to any benefit they had gained but was interrupted by Labour MPs, pointing out that the reverse had come as a shock to the country and the world.
Split into simpler sentences: Chamberlain began to make a case that actual Allied losses had been light and German losses disproportionate to any benefit they had gained. He was interrupted by Labour MPs pointing out that the reverse had come as a shock to the country and the world.