The X signs (St Andrews Cross) were illuminated signs that had a similar status to a platform signal. Hence they are also a type of fixed aspect stop signal. They mark the limit between the odd numbered (east/London) end platform and the even numbered (west/Taunton) end platform. In the photo, on the left hand side, in the foreground you have platform 5, beyond the St Andrews Cross sign, is platform 6. On the right, in the foreground is platform 3, beyond the St Andrews Cross sign, is platform 4.
There was a special signalling arrangement at Bristol Temple Meads. The signaller had two buttons for each platform face (one for the odd platform and one for the even platform). The signaller would operate the appropriate button depending on which platform the train was booked to call at. The appropriate signal at the gantry on approach to the station would then clear to an appropriate aspect and display an illuminated number, this number being the selected platform number. This was the authority for the train driver to pass the St Andrews Cross if the indicated platform was beyond the St Andrews Cross.
Otherwise, a driver would have to telephone the signaller for permission to pass the St Andrews Cross.
There was detailed information and instructions in the sectional appendix so that all staff who needed to know, were aware of these special arrangements.
All the St Andrews Crosses have now been removed. Proper colour light signals have replaced them.
