I got one (long) "interview" a while ago because I didn't file the GAR, due to an error on the GAR form airport designations.
I got another interview, very polite this time round, the other day upon return from a country which has some very old terrorist history with IRA connections. They also asked questions about N-reg planes, allegedly not carrying the same documents as G-reg - suggesting that somebody fed them the usual anti-N-reg disinformation, so I showed them the large wad of documents which an N-reg owner has to carry.
The Plod (who are of course reading this) certainly are acting according to some kind of strategy. No problem with that.
I just wish they dragged themselves into the 20th century and set up a website for entering the GAR information
A week's work for any half smart web programmer, and for that they would get a user database so if doing a repeat flight you could just login and not have to enter all the stuff again. A website which is just a dump entry form (with maybe a fax retransmission on the back end) would be 1-2 days' work. I know just the man to set it up..