fgwrich
Established Member
The announcement recently was that three extra sets are being converted and there's three sets already at Wabtec for conversion.
EDIT: there are some (more!) spare trailers for conversion as well, so might be them?
The set at Long Rock would tie in as being the third set though being formed of TGS / TSD / TS / TS. Given the recent delivery of vehicles from Long Marston (consisting predominantly of Porterbrook design TSDs) I would say they are the spare trailers and this may be the third set.