At the time of the Norman conquest, Thetford was the sixth largest town in England. Even in 1737 when Thomas Paine, the English-American political activist, author, political theorist and revolutionary, was born in Thetford, it was an important market town.
Everything that I attempted to visit in Thetford was closed either for the day (Art Gallery), or for unknown reasons (Priory) or rather permanently (Terminus Hotel).