Complex sentence: The Square is named after Robert Sidney, 2nd Earl of Leicester, who purchased four acres (1.6 hectares) in St Martin's Field in 1630; by 1635, he had built himself a large house, Leicester House, at the northern end.
Split into simpler sentences: The Square is named after Robert Sidney, 2nd Earl of Leicester, who purchased this land in 1630. By 1635, he had built himself a large house, Leicester House, at the northern end.