While he described the experience of shooting the cameo as "great," Sheeran also admitted that “I feel like people’s reaction to it sort of muddied my joy to it."
That's a shame. Sheeran also revealed that part of the reason why he attempted the surprise cameo (which, as it turns out, co-star Sophie Turner accidentally revealed to Williams before shooting) was because Arya Stark was originally supposed to die that season.
“She’s always been awesome,” Sheeran said. “I don’t think they had written the ending yet. It was meant to be her last season, but it wasn’t. And as a surprise for her, [they got] me on. So, she was meant to turn up on set, and I was by the fire.”