The Protofour concept was developed in the late 1960s and set out track and wheel standards as close in accuracy as practical to a true scale 4mm scale reproduction of the UK standard gauge prototype track.
It was a concept developed and introduced by the Model Railway Study Group (MRSG) who started the Protofour Society to assist in its promotion. The MRSG arranged for components to be marketed under the trade name Studiolith, trying to keep close control on production to ensure that the concept did not suffer from supply of poor quality parts. This policy backfired somewhat as demand increased and Studiolith could not keep pace.
The Scalefour Society evolved in 1975 as a breakaway from these constraints, whilst retaining the basic dimensional principles and concept. Eventually the two Societies were reconciled and merged under the Scalefour name.
The Scalefour Society remains the primary custodian and promoter of the original P4 standards, supporting the use of accurate scale wheels on a track gauge of 18.83mm for UK standard gauge, and 21mm for the Irish 5'3" gauge. P4 principles have also been applied to other prototype track gauges modelled at 4mm scale. The Scalefour Society also encompasses the overall concept of finescale modelling - models built as closely to true scale dimensions as is practical, and operated as authentically as possible.