| What incentive would the author have to talk with the police (let alone invite them into his home) in this instance? I understand that the police in the UK may not be as menacing as they are in the US, but if nothing is in it for him (and as far as I can tell, nothing was), then why would he allow himself to be questioned in such a way?

Incentive boils down to negative externalities:

* In the UK, understanding is attempted by the police; in this case, they probably received a complaint, heard out both sides, and made the judgement call of case having no legal basis. Not hearing the cops out have a potentially significant downside, in them understanding the situation incorrectly.

* In the US, the same level of understanding requires the interplay of a prosecutor, a defense counsel, and a judge (on top of the contestant & defendant), and several man-days of sweat. Talking with the cops can, by law, only weaken your position: anything you say can only be used against you.

The cultural trade-off is a question of variance: the UK system presumes low-variance situations, such that understanding can be built by reasonable individuals; while the US is geared to being tolerant towards people living on the edges, at the cost of longer due process.