Illustrative example
A tenant has rented the same flat through the same agent for six years. They want to bring a disrepair claim and have asked the agent three times who owns the building; each time they are told the agent is not permitted to say.
The duty in section 1 falls on the person in front of the tenant - whoever demands the rent, last received it, or acts as agent - and not on the landlord, which is the whole point of the provision. The fact that decides whether the clock has started is whether the request was in writing: the twenty-one days run from receipt of a written request, and three phone calls do not begin them.
The tenant sends a short written request by email and post; the agent supplies the landlord's name and address within a fortnight and the tenant agrees to route the disrepair correspondence through the agent as before.