Thank you all for the excellent selection of informative posts! So, from what I have read here, it seems to be possible for two 20' tanktainers to be loaded up to around 30 tonnes gross each, and conveyed at the maximum permitted speed on a 60' flat wagon with the middle position left empty. That would imply that the tanks are not full. In that case, what stops the liquid inside from “sloshing around” and destabilising the wagon? Are they fitted with baffles of some sort? And can anyone say when, approximately, tanktainers began to be used in the UK? Thanks again.