Complex sentence: Thereafter their behaviour changed so markedly that he toyed with the idea of writing to the Minister to visit him periodically but not to disturb the Minister, just to sit in his waiting area for a while and go away.
Split into simpler sentences: Thereafter their behaviour changed so markedly that he had to toy with the idea of writing to the Minister to visit him periodically. He would, however, not disturb the Minister, just sit in his waiting area and go away.