After October 2008 and the Post and Go machine printed stamps on demand launched in Bristol, then February 2009 and the new security measures:
If the slits are visible, you have to scrutinize the stamp to see the security printing waves in the name of the postal operator on the blue background (easily visible on the white of the value) and on the royal portrait.
Now, Ian Billings of Norvic Philatelics reports the first day of an experiment. At the Camden High Street post office, starting 8 June, the saint effigy with waves, intermitting slitted frame and simulated teeth illustrates the paper on which postal counter's Horizon meters are printed (the Horizon labels are currently printed on white adhesive paper). Like that:
Postal clercks are to use these labels only to stick them themselves on express letters, when consumers will ask for a special delivery service (with arrival guarantee the next day before 9am or 1pm), for 4.95 pounds sterling.
No label are to be given to a client. They must only exist printed with postal mentions and uncancelled (except for the first days produced by Norvic Philatelics et Brian Sinnott), and to be stuck to the departing letter.
If the Camden experiment is successful, many means to mark the payment of a postal service will bear the effigy of Elizabeth II by Arnold Machin.
For philatelic tourists, after the visit of the automated office in Tudor Street, you will go at 114-120 Camden High Street. This Northern Central London post office is located south next to the Underground Camden Town station, around two kilometers north-east from Saint Pancras railway station and at five hundreds meters from the north eastern entrance of Regent's Park. Prepare to send your envelope to an adress in the United Kingdom because only the 4.95 pounds special delivery service is part of the experiment.