[jmnicolas]

If you're doing low profile onenighters there's about zero chance to be bothered about it. Source : I did it a long time ago, I crossed France with my backpack from east to west then went in England.

Only once a woman asked me what I was doing in her field, I asked politely if I could stay the night, she said one night is OK and that was it. The only reason I had this encounter is because I was so tired that I didn't bother to look for a hidden place. I just built my tent in the middle of her flat field.

[robopsychology]

If people are considering doing this either camp after sunset and be gone before sunrise or knock on the farmhouse and ask if you can camp in the corner of a field in their land. 99% of people will say yes and appreciate you asking (you might get some free food out of it too!), and the 1% who do care will be pissed if they find you which you want to avoid anyway.