These were posted on Sunday using the EQUIPMENT TEAM TEMPORARY self-inking datestamp, index 32. We are unaware of any first day covers prepared on the opening day.
This flyer was available at the Post Shop and had, presumably, been distributed around the market and maybe the wider area. However the people at the permanent Camden Post Office didn't appear to know anything about it! (Click on the image for a larger view.)
And some Hytech receipts, showing that two of our contributors were using machine A4 within 20 minutes of each other! Thanks to all.
We understand that there is also a Smilers facility with a background picture of Tower Bridge.