HS4000 1969-10-23 near Aycliffe
During its brief spell on normal passenger service with the 07.55 KX-NewcastleA splendid picture of the unique Kestrel , equipped with the most powerful single Diesel propulsion unit in service , the sixteen cylinder Sultzer , which in theory would have provided a potential maximum speed of 125 miles per hour . Designed and built at Loughborough by Hawker Siddeley in collaboration with Brush Kestrel entered service in early 1968 but soon proved to be far too heavy for high speed running on express passenger rosters , a problem which persisted throughout the locomotive's short working lifetime with British Ralways and which thereby restricted it to freight duties , initially working exceptionally heavily loaded freights between the Nottinghamshire coal centres and Whitemoor yards at March in Cambridgeshire. In an effort to reduce weight Kestrel's bogies were replaced by two lighter units in mid 1969 thereby enabling the locomotive to work express passenger rosters as had been originally intended on the East Coast Main Line for a brief period of time before a return to its mundane coal train duties the following year . A transfer to Hull Dairycoates Depot in March of 1970 , from where it worked on freights from Humberside to Stratford was followed by yet more coal train rosters , the locomotive finally ending service in mid 1971 when it was sold to Russia.