As it's Canonical, they are a privately-held company:
https://find-and-update.company-information.service.gov.uk/company/06870835
So my usual advice won't apply.
- If it's a publically-listed company, buy one share before you apply for a job there.
This becomes your Right-To-Sue-As-A-Minority-Shareholder, and everything the staff say to you is admissible evidence. :D