Weasley - I wondered that, but the venue is actually in a public area (think Brighton Pavillion but not, iykwim). It could have been that the aforementioned guest was just walking through.
I'm still hoping no one did it. Sorry if that sounds mean, I don't want someone's wedding ruined, but gluezilla really should learn from this. There are still no photos that I've seen that show anything of the wider room, just group shots.
I'll see you all back here in a couple of years for the inevitable baby shower debacle. 