Info needed: Trailer socket Humber one ton

[Robert Sexton]

Thanks Richard, I had wondered if the drilled cross bar at the rear of the trailer was for another hitch as my trailer had the threaded piece to screw on the socket cap. I discarded the idea as not being practical, but subsequent pics and your confirmation proves otherwise.
The socket at the front of the trailer;was that used to connect to the towing vehicle via a piece with two male ends or did it have another purpose?
I have seen pics of trailers that look to have the connector permanently wired in as is with modern conventional trailer leads, if that was the norm then why the female socket on the trailer?
thanks for your help,
regards Robert.