Having looked at the marriage certificate,
(after some edoocashun by dawnsh - Thanks Dawn!)
and another 100 certificates "either side", then of course some people would put their work location down. Police, bakers, publicans, shopkeepers all do it, and more.
I also found an address, for a poss railway man, followed by "BWR" (note not GWR)
and a separate address, for a non-railway man, ending in "KT" (which I took to mean Kentish Town)
So, found loads of "A"s, and examples of "T"s written the same way
Therefore AT is not unreasonable, and bearing in mind GNR, then my original suggestion is my vote = AGAR Town (on the site of the railway development).
Did anyone notice that her father is noted as a "Vet" and the VetCollege is "opposite the church". Yet, the previous census he is a blacksmith. Was she "talking up" her father's occupation?
For interest, 1851 census link is MaryAnn, Richard her father, AND Amelia her sister (witnessed m.cert)
Ray