I rent my home from a Private Landlord, rent is paid by monthly DD to the Landlords Agent. I have never met the owner, all contact has been via the Agent, so I would get your relative to contact Agent ASAP!
We let a property, via an agent, and, although the payments are made via the agent, they are checked each month. The only reason for the landlord not chasing the rent I can think of is that the he is either not alive or not with it?
You asked why is he getting away with it? well he isn't getting away with it, he has defaulted on his payments and it hasn't been noticed yet.
I hope that your relative has been putting money aside as one day shortly someone will come knocking.
The problem might lie in three directions. A rather sloppy agent who is possibly not doing sufficient checking, a property owner who as a rather large portfolio and is reliant on their agent, and a rather sloppy tenant who as got away with things in the hope that they will continue. Nothing like living rent free?.
Whatever the case, the agent or the actual property owner will eventually find something wrong, and then take action.
There is also another possible twist in the tail. When the buy to let became very popular, many purchaser's bought the property on a mortgage arrangement, in the hope that the tenant would cover the mortgage. Some owners diverted the cash, and the mortgage payments ceased. The end result was a sudden visit by the mortgage lender with an eviction order?.