Diversion of a plane carrying a head of state, to be precise.
But yeah, it's not easy to imagine how such decisions are made. Of course, it's one of the features of authoritarianism that the display of authority trumps "tactical mistakes". But it's people who give such orders, not "authoritarianism". The simplistic explanation would be to state they're "pissed off". But maybe reality is quite close to that. By arresting Greenwald's partner, the UK authorities primarily demonstrate, to themselves, that they still hold certain powers -- and I wouldn't underestimate the self-motivational dimension of such a demonstration.
I don't think the UK government is just a US puppet here. A lot of materials that Snowden released are directly related to UK interests -- part of which is to at least be perceived as an autonomous entity that can make autonomous decisions.
I think it would be foolish to underestimate how closely the interests of the Five Eyes (http://en.wikipedia.org/wiki/UKUSA_Agreement)
track together. They were all hurt by the Guardian articles.
FWIW, this sort of behavior was expected from the UK and US authorities. They did the same to @ioerror and will likely do the same to any individual who is seen as challenging the interests of the US and UK intelligence organizations.
If you've de-cloaked yourself as an investigative apparatus that's dedicated to exposing the secrets of folks who expressly do NOT want their secrets exposed, you should expect no less.
But yeah, it's not easy to imagine how such decisions are made. Of course, it's one of the features of authoritarianism that the display of authority trumps "tactical mistakes". But it's people who give such orders, not "authoritarianism". The simplistic explanation would be to state they're "pissed off". But maybe reality is quite close to that. By arresting Greenwald's partner, the UK authorities primarily demonstrate, to themselves, that they still hold certain powers -- and I wouldn't underestimate the self-motivational dimension of such a demonstration.