No Paxman built engine fitted in a locomotive was a success on British Railways.
They were all diabolical and none survived more than ten years.
However.The Valenta engine fitted into the HST power cars was undoubtedly highly successful. They have almost all been replaced by a modern MTU machine.
English Electrics on the other hand were highly successful. Class 40s and 50s a testament to this and also the smaller 20s still in use today fifty years old. There is still a small army of shunters with EE engines fitted.