Organisation
There is certainly an organisation there, it's called the BBC, but it has extremely limited legal powers. Its strategy is to pretend to be an official agency with some official powers and it plays on the fear and gullibility of the Public. It's a shameful hoax - don't fall for it.
Letters
TVL letters ("threatograms", "hollowgrams") are a hoax on the theme of official letters. They are not official, have no basis in law, are misleading and threatening and are designed to underpin other aspects of the overall subterfuge.
Home Visits
Even the BBC calls these "Home Searches" when it's being frank. They are a breach of so many legal principles and laws. Even when the BBC claims that they operate with consent it is untrue. Ultimately, they have no right to conduct a fishing expedition at your home. You have every right to ignore them, to tell them to go away, and if they do not leave to remove them (with reasonable force in English law). If they remain after being banned or told to leave, then they are Trespassing and can be sued to claim damages and to assert your legal right to privacy.
Interview under Caution
Even their warped version of the Interview under Caution has problems - namely that they seek to hoax you out of your legal rights. Once they have cautioned you, tell the TVL operative to cease questioning and leave. Ignore anything they say to the contrary and quote PACE Code C Section 3.22. You also have the Right to Silence and the Right to consult a Solicitor, and you can use them too.
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