He worked in the assembly shop and the drawing office to get an all-round feel for railway life, giving him the experience to generate his own ideas.
When the Churchward development programme of new locomotives began to slow down, Holcroft sought employment with a railway still in need of original design work.
He joined Richard Maunsell's design team as an Assistant, participating in the latter's contributions to the SECR and Southern Railway's motive power.
This was necessary in the case of the SECR / SR Moguls because there was insufficient space for Holcroft's original gear to fit between the cylinder leading wheels and first drivers.
A collection of Holcroft's papers is archived at the National Railway Museum, and includes the manuscript for a second autobiography entitled Life with Locos.