New hobby I've developed when I have nothing to do at work is looking up dodgy looking spare room listings, checking their licences and if they're in breach reporting them (which can lead unlimited fines)

Take this listing for a room share with 5 other people (the flat is listed as having two bedrooms so presumably the landlord is in one and everyone else in the other)

Denbigh road is served by postcodes UB12RR and UB12RP but checking the Ealing council property register doesn't show any properties in those areas licensed to house that many people (because you'd never get a licence to do that)
https://ealing.metastreet.co.uk/public-register
You can check for yourself here

Now it's just a quick online report and on to the next one!