I would like to highlight here what an anonymous poster mentioned in a comment to our earlier post about the new security features to be added to some Machins.
The 50p and £1, along with the current high values £1.50, £2, £3, and £5, will also get the new security features, which are:
1) Four small semi-circular slits that prevent the removal of the stamp from envelopes
2) Iridescent ink featuring a security pattern on the background of the stamp
3) Printing in self-adhesive format only. For high values, that will mean self-adhesive sheets of 50 replacing the water-activated gum sheets of 200.
As the poster noted, it seems strange that the high values are being subjected to this treatment, since they are not on general sale and not frequently used anyway. We don't see piles of uncanceled £5 stamps offered on eBay (do we?).
Of course, cynics might say that the only reason to do this is to sell the high values to collectors - again! But we don't have any cynics writing this blog. No, definitely not.