The British Rail Class 43 HST, also known as the InterCity 125, is a UK High Speed Train.
The class were built by BREL at Crewe works between 1975 & 1982 and to this day they remain dominant on many mainlines in the United Kingdom.
They are the fastest diesel locomotive in the world, with an absolute maximum speed of 148 mph, and regular service speed of 125 mph.
All HSTs in this video are installed with MTU 16V4000 engines, which replaced the Paxman Valenta 12RP200L.
Here is a selection of clips I have of the HSTs at speed in many different locations on the East Coast Mainline such as: Stevenage, Huntingdon, Peterborough, Grantham, Newark Northgate, Retford, Northallerton, Durham, Chester-le-Street & Alnmouth for Alnwick.
All trains in this video are running at speeds between 50mph & 125mph.