Sentence:  Unlike the students, <WSD>Principal</WSD> Robertson, who now resided almost alone in the College, continued to use the accistomed route on his visits to the Old Town; and it “became the joke of the day that from being the principal gate it had become only a gate for the <WSD>Principal</WSD>.”5 
Meaning of the word marked with <WSD> tags:  The chief executive and chief academic officer of a university or college.