Sure, total sterility isn't really achievable, but I don't think inspections even expect that. Honestly, I'm not sure exactly what criteria they use to judge cleanliness. But either way, there's daily cleaning by staff to handle surface-level dirt. Grease, carbon buildup, leftover food scraps piling up in hard-to-reach spots, that's a job for professional commercial kitchen cleaning in London, which needs to be built into the schedule as its own separate process, not just a one-off "just in case" thing. With that kind of routine, where something is actually being done every single day to keep things clean, you can pretty confidently pass an inspection.