[sjhoward]

I suspect that’s more the uk politicians don’t like to be scrutinised for those sort of lengthy periods!

Perhaps I'm being too generous, but I think it's more subtle than that. It is not at all uncommon for TV interviews to be clipped down to a few seconds, often on the basis of something embarrassing happening or some other occurrence that is irrelevant to the purpose of the interview. This can make them unduly risky.

Long interviews with politicians still happen, just less often on camera than was previously the case. For example, it's not at all uncommon to see politicians sit down for long-form print interviews (think Sunday newspapers or news magazines or Lunch with the FT) and, perhaps a bit less commonly, long-form radio interviews (think Political Thinking with Nick Robinson). Outlets that a politically aligned with the politician are also less likely to give them a rough ride, of course.