Just found something interesting on a Facebook group I'm in concerning Edinburgh, not Newcastle, but the idea is the same. On the site today is a telephone exchange, however this fascinating photo exists of a boxing booth itself.
"What was on this site previously was an open area for Carnivals, Fairgrounds, Boxing Booths and many other types of entertainment. The Boxing Booths were a source of income for many unemployed men who were brave enough to take on the professional boxers as a challenge. There was also exhibition boxing matches some featuring the well known Leith boxer Tansy Lee and the renowned Paddy Fee."