My question: Does Perverting the Course of Justice 'apply' to those who try and garner 'evidence' using somewhat deceptive means, even if the evidence they intend to gain is accurate and lawful?
John has a need to prove his employment history. Perhaps he is being questioned on it by his current employer and that employer is threatening to go through with civil action. This context is irrelevant really.
John then decides to ask his employer to write a reference in case any future employers come asking for one. He isn't looking for a job. The ex-employer agrees and states something along the lines of 'certainly, you always were a great employee' - the proof John wanted to prove that he worked at this place all along.
The example is a little backwards, not making much sense in the real world, but I hope you understand the point I'm trying to get at. Is it illegal to lie or deceive in order to gain evidence?