Travelling exhibition. Presumably, many destinations to be added to the schedule. (This is another reason why a terminus needs multiple platforms, it'll be disappointing if the Inspiration Train doesn't rock up at Newquay.)
It seems to miss out the current
GWR▸ territory completely ... Moor Street and Severn Valley Railway are sorta-close. Wouldn't it be nice if they laid a platform for it to visit at Westbury, where people can visit from 6 different directions, then leave the siding as a legacy to be used to ease congestion at the station and improve services for years to come.