John Knox, the house and the hat

Yesterday, as part of the graduation ceremony No 1 son was “doffed” on the head with “the graduation cap”, a black velvet hat supposedly made from the breeches of John Knox
I have seen this building on the Royal Mile before, but today it took on more significance when I saw it was John Knox House.   It dates back to 1470, which makes it (and the adjoining building) the only original medieval buildings surviving on the Royal Mile.   Its survival can be attributed solely to the fact that John Knox lived there for a few years before he died  
 I thought I had better find out who this John Knox character was.  He lived  c 1514 - 1572, was considered one of the most powerful preachers of his day.  He is a key figure in the formation of modern Scotland.  In a relentless campaign of fiery oratory, he sought to destroy what he felt was idolatry and to purify Scotland's religion resulting in the Scottish Reformation, the outbreak of civil war and the abdication of Mary Queen of Scots. 
This means the hat is pretty old and I wonder how many students’ heads it has doffed.  I have added an extra for yesterday of the moment No 1's  head was doffed