Yes it is London, 1790, but the maker's mark is difficult to decipher. It looks as if it is one mark overstruck on to another. Is it possible to disentagle the mark, perhaps with a close up picture?
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Looking through Jackson's for th relevant period, the closest I can find (based on the particular shape of the "G" in the top right corner and the partial (possibly) "w" underneath, is Samuel Godbehere & Edward Wigan who are entered in Jackson's for 1786. (PLEASE NOTE - this is just a speculative guess without a better picture and really solely based on the "GE" which does appear to be a correct match)
Please post a better picture of the maker's mark - try using a magnifying glass underneath your camera...you'd be surprised how clear you can get it if you have the dexterity to move the magnifying glass and camera (and zoom lens!!) in and out!. Try it and sent it on - this is one I really would like to get a better picture of because as things stand, I cannot understand why there appears to be a double strik.