HS4000 , named Kestrel , was a prototype high-powered mainline diesel locomotive built in 1968 by Brush Traction to demonstrate its wares to British Railways . The name came from Hawker Siddeley ( the owner of Brush ) 4000 hp ( the power rating of its Sulzer engine ) . HS4000 , named Kestrel , was a prototype high-powered mainline diesel locomotive built in 1967 by Brush Traction , Loughborough as a technology demonstrator for potential future British Rail and export orders The locomotive number is a combination of the initials of the owner of Brush Hawker Siddeley and the power rating of its Sulzer diesel engine ( 4000 HP ) .