If those working at the Stock Exchange wanted to send a telegram they would, if they followed usual procedure, write their message on a telegram form and take it with payment of one shilling or more to a clerk who would then give them a 1 shilling green postage stamp to apply to it, with other stamps if needed to make up the correct fee, which depended on the number of words.
From investigations carried out by Dr. Ian Ray, it seems likely that a head clerk named George E. Smith colluded with his subordinates T. H. Wright and Benjamin Hind to affix the bogus adhesives to forms.
Almost four decades after the known dates when most of stamps were sold, Wright and Hind had died, but Smith was still alive, having retired from the post office in 1870s on the grounds of ill health.
The fraud was not detected at the time and could have remained undetected had all the stamps been destroyed as originally intended; however, they were retained by the Stock Exchange for a period, after which they were disposed of as waste paper.
As a large number of forged stamps were certainly made and as 1 shilling was a more significant sum at the time than it was later in the 19th and 20th centuries, it is likely that the fraud was highly profitable for the culprit(s), who were never identified in their lifetimes.