Just out of interest really, but does anybody know what rules are applied to determine which cabin a UK domestic connection is ticketed in when flying long haul in premium economy? I know a while back (before business existed on domestics) there was a "UK Business" designation which provided lounge access, but since business was introduced I've only ever seen the domestic sector in economy, regardless of the booking class for the long haul leg.

I've just booked flights for next week to Dallas from Newcastle, and noticed that the connections are both in business which seems to be new. I've done some dummy bookings to test this out and it broadly seems to be that a connection is in business if the long haul premium economy costs lots of money, but the connection is economy if the long haul element is not lots of money.

I'm therefore assuming that certain premium economy booking classes will now generate business connections, but just intrigued whether anybody knows where the line is drawn and when this was introduced?