I know someone who has purchased a house. The seller said that they
have been looking after one of the sheds adjoining a communal yard
even though he knows it actually belongs to his neighbour. He signed
an affidavit saying he had looked after the shed for the past 5 years
and then said if the purchaser were to continue using the shed for the
next 7 years then providing he isn't challenged and is quite open
about using it then the shed becomes his by law.

I am aware of the laws regarding adverse possession and nec vi, nec
vi, nec precario and all that, but this seems to be a bit
surreptitious, kind of conspiring to possess.

Any thoughts?