On the GWR, there was an extended period between political intervention in 1846 that prevented major expansion of its broad gaugeThe Act of Parliament did not prohibit expansion of the existing broad gauge system, but it had the indirect and delayed effect of forcing conformity with the "standard" gauge eventually. and the final gauge conversion to standard gauge in 1892. During this period, many locations practicality required mixed gauge operation, and in station areas the track configuration was extremely complex. This was compounded by the common rail having to be at the platform side in stations; therefore, in many cases, standard-gauge trains needed to be switched from one side of the track to the other at the approach. A special fixed point arrangement was devised for the purpose, where the track layout was simple enough.S.C. Jenkins and R.C. Langley, The West Cornwall Railway, The Oakwood Press, Usk, 2002, ISBN 0853615896, gives an illustration and description on page 66.
