Drivers of trains speeding west through Castle Cary can't see the signal at the far end early enough due to the footbridge and buildings so this banner repeater signal is situated at the east end of the platform. It has two signal heads so that the driver knows if the signal for the main line or for the junction to the left (the Yeovil line) is 'off' before they can see it.
<a href="//commons.wikimedia.org/wiki/User:Geof_Sheppard" title="User:Geof Sheppard">Geof Sheppard</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>