The file is the 8th segment of a multi-part compressed archive created with 7-Zip .
: You cannot open "piece .008" individually; the decompression software needs the header information typically found in the .001 file to understand how to put the puzzle back together. UK-PD Plan.7z.008
: Ensure you have every file in the sequence (UK-PD Plan.7z.001, .002, ... up to the final number) in one location. The file is the 8th segment of a
: Select "7-Zip" > "Extract files..." or "Extract Here." 7-Zip will automatically detect the other pieces and reassemble the original file for you. UK-PD Plan.7z.008
: Right-click on "UK-PD Plan.7z.001" (the first piece).