If the person is a Camden Council tenant then they have certain obligations: http://camden.gov.uk/ccm/content/housing/council-tenants-and-leaseholders/file-storage-items/the-tenants-guide—information-for-tenants-of-camden-council-homes.en and in particular page 130 of the PDF attachment listed there. It’s in the section about tenancy conditions. Contact Camden (020 7974 4444) will then have the right escalation details for you.
To be honest I don’t know if this also applies to leaseholders (I think there may be some provision) or privately owned properties, so it depends on who their landlord is, and whether they are definitely a tenants. We’ve a guide here that helps works out who is a leaseholder: https://www.leaseholdersforum.org.uk/guides/finding-fellow-leaseholders/