A post-war design (in fact, this was the last LMS steam locomotive design) intended as a replacement for older freight locomotives, the look of this locomotive owes a lot to the American class S160 locomotives used during the Second World War, particularly with a high running plate leaving the wheels completely exposed.   The locomotive was designed for ease of use and ease of maintenance, post-war conditions meaning that designers had to take more note of the human element of locomotive operation, something that had been perhaps
 
Technical Data
 

Introduced : 1947
Number built : 162 (3 built by the LMS, the remainder being built by British Railways)
Wheel arrangement : 2-6-0

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Ivatt Class 4F/4MT

Class 4MT no. 43106 at Kidderminster, Severn Valley Railway, 31st December, 2013

 

Number

Location Built

Built

3000-3002

Horwich

1947

3003-3010

Horwich

1948

43011-43022

Horwich

1948

43023-43049

Horwich

1949

43050-43096

Doncaster

1950

43097-43111

Doncaster

1951

43112-43135

Horwich

1951

43136

Horwich

1952

43137-43155

Doncaster

1951

43156-43161

Doncaster

1952

Preservation
 
The only member of the class to survive into preservation is the one seen above, 43106.    This was built at Darlington in 1951, so is post-LMS, and would not have carried any of that company's liveries.   Bought directly from BR by the Severn Valley Railway, it currently operational on that line in a BR Black livery.
43106_62061.jpg
lacking in the designs prior to 1945.  Initially the class suffered from steaming issues caused by the exhaust arrangement; the class initially being fitted with double chimneys.   However, by 1951, the issues had been ironed out, particularly by replacing the double chimney with a single one, and the locomotives proved very capable from this point on, the last withdrawal taking place in 1968, over twenty years after the first one was built.
 
They were perhaps not the most aesthetically pleasing of locomotives, with some opinion saying that they were the most ugly locomotives after the Southern Railway's Q1 freight locomotives introduced during World War II (One nickname given to the class was "Flying Pigs").   However, this was a time when aesthetics sometimes had to take a back seat to functionality and economy, and personally I quite like the design and am always happy to travel behind 43106. 
 
The Ivatt designs could often be found outside the London Midland Region of British Railways, and the 4MT was also used on the Eastern and North Eastern Regions as well.   The design eventually evolved into the 76XXX class of British Railway Standard Locomotives.