Trainman 864
Registered
By the early 1970's, something appeared to change as regards the regulations, so locos with exposed running gear then became the norm until the lines were closed.
I know that "unskirted" locos did certainly get onto Ipswich Docks prior to this as there are a number of photos around showing them there, including a J67 (I think...) running as a 2-4-0T to enable it to get around some of the curves!
Maybe sometime prior to the 70's it had become common practice to leave off the skirting to make maintenance easier - especially as the docks did not pose the same level of danger as running in public streets.
And then the regulations were amended to bring them into line with what had become the norm.