In Commonwealth countries, under British Common Law, a person may adopt any name they wish (as long as it is not for illegal purposes) which was convenient since I 'transitiioned' long before there was any legal avenue to change anything, so I simply sent an advisory letter to where ever there was record of my name with the instruction to change it. For government records, where sex was also recorded, I sent a copy of the surgeon's letter with the instruction to also change the gender. Birth certificates (here) were among the last documents that could legally be changed.
So yes, from even before the first day of transition, everything was signed by my proper name. (From my teens onward, I had used only my initials and family name so it was actually a small change.)