I think this letter was sent from "I T Ives" though I am not certain as I can't quite make out the signature. Perhaps another letter from the same individual will appear from the boxes and offer me another clue.
Isn't it interesting the complete absence of punctuation throughout the letter?
Most curious to me was the word "quinseys." Not a word I've ever heard before but clearly related to an illness as "she has not had them since." A little google research and I discovered that "quinseys" were peritonsillar abscess (PTA) a rare and potentially serious complication of tonsillitis.
115 Bride Street Barnsbury London
Dear Mr and Mrs. Pinborough - Just a few lines trusting this will find you all well as I am happy to say this leaves us all at present you must have thought I had quite forgotten you after all this long time but I can assure you such is not the case but I only found your address yesterday on your last letter dated March 20th 1913 so have not lost much time now I hope your little son is getting on all right I suppose you have given away all those pictures of yourself and baby by this time I have not heard from Newmarket since we are still going on in the same old style still got the little shop and I am still working at the same job it was a most unfortunate time when you called that my wife was so queer with the quinseys but am glad to say she has not had them since you must please excuse short letter this time but just enough to let you know that I had not forgotten a Sincere Friend I ever remain your sincere Friend with love to all - I T Ives