This is the design of the temporary suspension sign that Hounslow use. It was approved by the DfT in 2011. It is intended to be folded along the red vertical lines to form a triangle around the post.
The argument here is about whether the sign is valid if the centre panel with the dates is facing the pavement. If that happens then both end panels are facing the road, making it quite clear to drivers that this is a No Parking sign. It is only misleading to the extent that until you read the centre panel, it appears to apply to all dates and times. So don't park there without confirming that the centre panel allows this!
Diane asked me about the PCN last November. When it became clear that there were two suspension signs on the same post, and that she had ignored the one relating to the day in question because the centre panel was facing the pavement, my advice was that the sign was still valid, and that she had no viable defence.
Nevertheless Diane showed her determination by continuing to appeal again to Hounslow and then to an adjudicator at London Tribunals, sadly without success.