I have been looking for a 1948 for fifteen years with no joy. Skennerton in an earlier book published that the No.5 production ended in October 1947 based on a gun now in my collection. I later found a December gun and it was used as the basis for the revised date in Skennerton's last book. I have asked abut a 1948 of and on for many years in the various forums with none found todate.
A chap on gunboards posted pictures of a 1948 probably 2 years back. I'll do a search and try to locate it.