A man has been "cautioned" by police - What does this mean in the UK?

That’s what I said about English/Welsh law, but incorrectly implicated Scotland (and NI) by saying “over here”.

There have indeed jjimm been significant changes to this central plank of English criminal process.

Section 101 of the Criminal Justice Act 2003 permits submission of ‘bad character’ evidence, including previous convictions if any one of a number of conditions are met. These include whether such convictions are ‘important explanatory evidence’, or that it is ‘relevant to an important matter in issue’ (eg. whether the defendant actually committed the offence!)

It seems worryingly broad, although the judge does have discretion to exclude evidence if s/he believes to admit would have such an adverse effect on the fairness of the proceedings.

As always the law is a bit more convoluted than that, so by all means have a read of the statute if you’re interested.