We knew in the first season of Game of Thrones that Ser Jorah Mormont was spying on Daenerys and sent the news about her pregnancy to King's Landing, prompting Robert Baratheon to order the baby and Dany executed.
Two seasons later in Episode 8 of Season 4 (few years after Robert's death of course) a letter, a Royal Pardon meant for Jorah Mormont is sent in Meereen which however is given to Ser Barristan by that child and learns that Ser Jorah spied on Daenerys for which she tells him to leave Meereen before she orders to have him executed.
The question is, who sent the letter? Ser Jorah says the letter is not forged, it's signed by Robert Baratheon and in the same year he meets Daenerys. So Robert signed it, but who sent the letter after years and how did he know they were in Meereen. The seal on the letter seems to be Hand of the King's seal, but who actually?