When Charlton and Serena exited the mansion leading to the backyard (yes, the polo field was part of the backyard), it was 30 minutes before noon but since the sun was hiding behind the clouds, it was not too hot.
Leonard, Annalys, and Emily were on the field riding their pony astride. Hugo and Hanna (Hugo's sister) were standing together in the Patio. While Christopher was not in the immediate sight.
Note that though there were only 7 people invited, there were more people present. After all, they were all noble personages of their own right and each of them sent servants in advance to bring their ponies.
Charlton excused himself to talk to one of the servants while Serena walked towards where Hugo and Hanna were.