"HS4000 ‘Kestrel’ was a one-off prototype locomotive built by Brush Traction of Loughborough, England in 1967. It was designed as a technological showcase to attract buyers from both British Rail and overseas, and with a power output of 4000hp it remains the most powerful diesel locomotive ever to run in service on British railways, and one of the fastest with a top speed of 125mph, predating the IC125 HST’s by around a decade."