We have talked a lot about the fact
IETs▸ on diversion are unable to call at Melksham. It has been suggested this is because the software hasn't been programmed to allow it.
At Par I noticed the sign below on platform 3 - the one normally used for the Newquay branch. However there is a route west towards Penzance which I imagine doesn't get used that often for passenger service (at the moment). However it seems to indicate it could be used by the longer IETs under a special arrangement.
Could this be a possibility for Melksham? A sign would be a cheaper option that a software upgrade, but are there other factors in play?