In his “Machin Watch” column in Gibbons Stamp Monthly of March, 2013, John Deering writes about a new batch of current forgeries that is in circulation. It’s a booklet of 12 of first-class gold stamps, no longer current but certainly not old enough to raise suspicions.
He calls these “astonishingly convincing” and notes that they have the iridescent overprint, though without the “MTIL” source code in the upper right and without a date code. He doesn’t mention whether side bands have a phosphorescent afterglow, although generally forgeries do not. From the photograph in the article, it is apparent that these stamps even have the little notch at the top and bottom of the U-shaped slits, which we call Type 2 in genuine stamps.
He suggests that in this case, collectors should put aside the desire to own these counterfeits, because they are so realistic that they might be inadvertently used for postage.
He also suggests that Royal Mail may be forced to develop additional security measures, even though the current ones are only four years old. It does appear that the current measures are not much deterrent to accurate reproduction, and I wonder if there is anything that Royal Mail can do without vastly increasing the cost of producing stamps.