Just noticed this. It appears to be an MOT failure now. No idea if this is old or new news but I know some of the diesel guys on here often warn of DPF issues on diesels.
https://www.gov.uk/government/news/new-rules-for-mot-to-test-for-diesel-particulate-filter
https://www.gov.uk/government/news/new-rules-for-mot-to-test-for-diesel-particulate-filter