My pedant friend says the guy was Richard ( Edward Lloyd ) Maunsell !
The Metropolitan 2-6-4 Tanks were virtually identical to the Rivers but were only goods locos so didn't run a the sort of speed where surging would be an issue : the Brighton Ls, though WERE found to be unstable ( BEFORE the days of he Rivers ) and had to have major modifications to their waterworks in order to lower the centre of gravity.