34 were rebuilt by Charles Bowen Cooke from Class A 3-cylinder compounds between 1909 and 1912.

Rebuilds of the troublesome Webb Class A compounds to Class D simple expansion engines used larger (5'2" diameter) boilers, with the result that there were many spare smaller (4'3" diameter) boilers available.

As a result, rebuilds of the Class As from 1906 retained their smaller boilers.

[1] When rebuilt from Class A, all the C1s retained their existing LNWR numbers, which were in the 18xx or 25xx series.

The LMS assigned them the numbers 8968-9001, sequentially in order of rebuild date, though not all were applied before withdrawal.