Here is an example of how to annoy TV licensing salesmen.
All TVL officers have an ID card. They cannot knock your door without one. You have the right to see it and you have the right to close the door while you phone Bristol to check it.
TVL: Hello, I'm a TVLA Persecutions Officer. Here's my authority. [Shows you his card.]
Objector: Do you mind if I just check this? It's just that we've had a number of bogus callers in the area lately.
TVL: Certainly.
Objector shuts door.
Phone up Bristol TVL and give them the details on the card. Ask if this card is theirs. They say it is. Meanwhile you are writing the TVL address on the front of an envelope.
Pop the card in the envelope.
Leave the house and explain you are just going to the shop and will be back in two minutes. The TVL officer will almost certainly pursue you requesting his card and may possibly call for backup. However, he cannot lay a hand on you. He will simply obstruct or pursue.
Drop the envelope into the post box and return to your house and await the police. Alternatively, if you have a post office nearby you can go there and they will stamp it for you.
Now, enjoy the aftermath.
If the police do arrive, the TVL officer will claim that you have stolen his card. Calmly explain to the attending constable that he gave you the card and that you have simply returned the card to the confirmed owner - ie. TVL, Bristol. This does not constitute theft, for which the legal definition is "To take some item without consent with the intention of permanently depriving the owner thereof."
The police won't be happy about it (unless they see the humour of the situation) but there's nothing they can legally do about it.
(Caveat: The police don't care about the law and may arrest you anyway - no charges will be brought however, and you will be released.)
I have used this on a number of occasions and it's always worked like a dream. If they try to physically restrain you, simply point out that they are assaulting you - in a loud but polite manner, making sure that others notice your protest.
Better still is if you have a family member leave and post it for you whilst he stands at the door expecting your return. Then you can politely inform him that if they rush they might just catch it before it's posted. The look on their faces is just fantastic.
The great thing about this is that if they don't have a spare (and in my experience they never do), they have to quit for the day - in fact, until they get a new licence printed or the old one arrives. Always use second class post. Never use the postcode!
Always great fun.