It's not that complicated. The previous Great Prince sent an embassy to London to establish trade relations and to marry off one of his numerous princesses during the past turn. LightFang was apparently only happy to agree, but reluctant to give her the Heir Apparent, Arthur, because of some standing engagements with Spain. I pondered the amusement value of giving Henry VIII (the other choice) a head-start on his, ahem, married life, but nonetheless argued that that those standing engagements were far from set in stone at the time. Then he left and you took over, and the ambiguity remained unresolved. So?
Your princess got Henry III.