Travelling very slowly, having nearly caught up with the 1K50 11:49 Reading to Bedwyn DMU, 43154 leads the 1Z10 11:33 Paddington to Paddington (via Frome) special past Brimpton on 14 May 2016. Making no stops other than the reversal at Frome, this is obviously something out of the ordinary. I presume it is a crew training run. Confirmation anyone?