I knew the chap who did it, Peter, and it was literally a "bloke in a shed" type job. He passed away about a year or so ago and he use to mention it from time to time. It was a fairly simple job to lock the front wheels on beam axils, I believe, and was often done when people used an old front axil when making a trailer.
I don't know what would happen if the front wheels were not locked but there could be problems when going over points?