Complex sentence: The British mountaineering establishment covered up the affair for over fifty years by pinning the blame on John de Vars Hazard on the grounds that, by deliberately deviating from the officially permitted route on his return to Sikkim, he was the cause the diplomatic incident.
Split into simpler sentences: The British mountaineering establishment covered up the affair for over fifty years by pinning the blame on John de Vars Hazard. They claimed that, by deliberately deviating from the officially permitted route on his return to Sikkim, Hazard was the cause the diplomatic incident.