In the late 1950's an experimental hopper was designed to replace open wagons which were labour intensive and take time to discharge in comparison to a bottom discharge wagon.
The prototype G 1 was trialled with great publicity. After the tests, the vehicle sat in storage at Newport Workshops, unused for 15 years before being scrapped in the early 1970's.
One story that was passed on was that ".. it discharged too quickly, faster than the conveyor system .. ( at the test site ) ..". Perhaps the expense of building and maintaining a dedicated "grain only" fleet plus unloading facilities may have been the main factor in not proceeding.