St Stephen's Gate postmill is just visible on the 1723 map. Mark Hayton was the miller in 1778, when the mill was insured.

Mark Hayton of the City of Norwich, Baker. On Furniture in his Dwelling House, Shop & Baking Office adjoining brick & timr. pannell'd with brick plaister'd over & tiled, situate in the Parish of St. Petr. of Mancroft in Norwich afresd., £50. Trade in the same, £50. On his Windmill timr. built sit. near St. Stephen's Gates belonging to Norwich aforesd., £100. On Trade therein, £50. On a House, Millhouse & Flour House adjoining brick & timber built & tiled, sit. near, Tent., Mefsrs Thos. & James Reymes, £50. On Trade therein, £50."
Royal Exchange Insurance policy 74323 - 21st November 1778

A WINDMILL
To be SOLD, a very good and substantial MILL, in good Repair, out of St. Stephen's Gates, the Road to Eaton, with all the Going-geers and Utensils, now in the occupation of Mark Hayton.
For Particulars apply to Messrs. Foster, Son, and Unthank, Attornies at Law, Norwich.
Norfolk Chronicle - Saturday 5th February 1785

The mill was not sold and was put up for auction a few months later

To be SOLD by Auction
By RICHARD BACON
On Friday next, the 27th day of May, precisely at Four o'clock in the Afternoon, at the WHITE SWAN, Norwich
A very good WIND-MILL, standing just without Saint Stephen's Gates, with a Dwelling House and Stable adjoining, together with about three Acres of exceeding good Land adjoining, on Part of which the above Premises stand.
The Land is Leasehold of the St. Stephen's Parish for a Term, of which about twenty-five years are unexpired, subject to an annual Rent of 10l.
For further Particulars apply to Messrs. Foster, Son, and Unthank, Attornies at Law, Norwich.
Norfolk Chronicle - 21st May 1785

John Buck snr. was the miller in 1801, when he was selling a post mill at Witton. He had previously been at Pockthorpe smockmill. He was listed in Peck's Directory of 1802 as being at 57 St. Stephen's St, and in the 1802 Norwich Poll Book as a miller in St. Stephen. He had a son, also called John, who was married on the 2nd March 1806.

To be Sold
An excellent Post_Wind_Mill in good repair, built about twelve years ago, with a Flour Mill, two pair of French Stones and all the going gears complete, also about half an acre of Land, adjoining and situate in Witton_Field near Blofield, the whole now in the occupation of Robert Hirst, Miller, under lease to him and another person for a term of years of which four were unexpired at last Midsummer, at the clear yearly rent of £21.
Apply to Mr. John Buck, Miller, St. Stephens or to Mr. Thomas Barber, attorney, Norwich.
Norfolk Chronicle - 5th September 1801

Sunday se'nnight was married, Mr. Buck, miller, to Miss Harrison, both of St. Stephens.
Norfolk Chronicle - Saturday 15th March 1806

John Buck jn. may have learned his trade at Keswick mills. John Buck snr. died on the 27th August 1816.

John Buck jnr seems to have taken over Lakenham postmill by this time.

William De Caux was the miller from 1830 to 1845. He was listed in Hunt and Co.'s Directory of 1850 as an oatmeal and groat manufacturer at St. Stephen's Gates. He died on the 19th February 1850

DIED.
Tuesday last, at his son's house, in St. Stephen's, Mr. Wm. De Caux, formerly a corn merchant of this city, in the 90th year of his age.
Norfolk Chronicle - Saturday 23rd February 1850

The mill seems to have been demolished circa 1848, its site being required by the Eastern Union Railway for their Victoria Station, which opened in 1849