Chapel Field postmill, in 1289, was possibly the earlist mill to be mentioned anywhere in Norwich.

The earliest mention of a windmill within the city is probably that of 1289 regarding a mill owned by the Prior of Buckenham, very likely the mill in the Chapel Field granted to Richard Spynk, a citizen of Norwich, by Prior Hugh a little more than 50 years later.
When Windmills Ground the City's Flour, R.W.M., Eastern Daily Press - 13th April 1970

Richard Spynk
completed the building and fortifying of City Walls and Gates, 1343.
For his Charter, 10 December 1343
Blomefield's History of Norfolk, Vol. III & The Records of the City of Norwich, J. C. Tingey, 1910

1289: Windmill owned by Hugh who was Prior of Buckenham from 1329 until his death in 1354