Background The machines were produced from NUMBER@1 onwards from the North British Class NUMBER@2 by replacing the original unreliable license-built MAN of the Class NUMBER@3 with ORGANIZATION@1 NUMBER@4 engine at PERSON@1 's LOCATION@1 works .

The original license-built MAN engines of the Class NUMBER@3 had proved unreliable , so in NUMBER@1 locomotive NUMBER@5 was sent to PERSON@1 's LOCATION@1 works to receive a new MISC@1 engine .
