It looks a bit like the CC Rowntree Park site in York where the EHU connections are 5-6 ft above ground because of the regular flooding they get there.
The Red Lion campsite between Tewkesbury and Gloucester has a similar arrangement. It is to prevent the connection box being flooded as the campsite may be on a flood plain?
Seen the same feature of elevated EHU outlets in France where sites were prone to flooding.
In the photo the amount of willow rather endorses the pictured site very likely has that issue.
At the showground in Kelso, the outlets are attached like that to the perimeter wire fence, makes sense as river tweed is next to it and is prone to flooding.