I was a bit shocked to hear on Feedback (Sunday 20:00) that while they don't select the audience, they do ask the hosting organisation to contact local political parties.
I'd have thought there would be enough members of the public interested (esp if notice was given in the local press) without political activists being tipped off about an event (and presumably making up the majority of the audience).
I had rarely questioned the impartiality of the audience (or randomness of political loyalty) but now I know, I will be more attentive when someone gets a portion of the audience either cheering or being negative about their comments.
I'm rather disappointed that they don't do anything to see how their audience is comprised (I don't expect them to 'veto' anyone but it might be handy if they gave out cards and did a quick analysis afterwards to see (a) what proportion were notified by a political party and (b) which party it was.
At least that way, when the second broadcast is made, we could know (via website or in the introduction) how many had stronger than average political ties!