https://en.wikipedia.org/wiki/TEP80
But in any case this was just for an unattached locomotive, not a train.
The 159 mph record is for a train of which only two were built and now are not in passenger service. But a record is a record.
The 148 mph is for the InterCity 125 or High Speed Train, a diesel-powered high-speed passenger train built by British Rail Engineering Limited between 1975 and 1982. A total of 95 sets were produced, each comprising two Class 43 power cars, one at each end, and a rake of seven or eight Mark 3 coaches.
On 15 May 2021, EMR retired their final two InterCity 125 trains. So none of the above record holders are now in regular passenger service.