They were not built in the LMS's own workshops, but by contractors in Birmingham, Metro Cammell, and Birmingham RC&W, both of whom had prior experience with building this type of train for the London Underground.
They were not built in the LMS's own workshops, but by contractors in Birmingham, Metro Cammell, who built the motor coaches, and Birmingham RC&W, which built the underframes. Both of whom had prior experience with building this type of train for the London Underground.