Except transit passengers on one ticket don't have to pay it, but transit passengers on separate tickets do. Again, as I posted upthread, HMRC makes the rules and that's how they've defined it, and so be it, but it is an irritating anomaly when you're on the wrong side of the line. Some countries I believe do levy passenger service charges on transit passengers based on the fact they will require some sort of state infrastructure during their transit (security screening and the like) but APD isn't in that category as it is only levied on ex-UK originating passengers, which but for the "reality" of the way the tickets were issued, I'm not.

Oh well, so be it for the price of using the 2-4-1.

including the UK as there is �39.75 UB tax when connecting in LHR...

I must admit I agree it is annoying. I wish there was a facility to treat it as APD exempt when you are on separate tickets but you are genuinely in transit with < 24 hours between flights.

On the other hand though I had a "weird" situation when flying on two separate tickets (it wasn't planned that way but due to my schedule change) on TK somewhere, I think it was SIN. When I requested to through check my bags, I was told that I had to pay �120 or whatever it was extra to do that. I was a bit shocked and queried why I was being charged for baggage. The staff were baffled too, but eventually tracked down what this was all about. As it turns out, the system said I had to pay the APD for SIN if I don't pick them up at IST and re-checked them.

It seems rather one-sided. If they charge me the APD on separate bookings going via somewhere, then I'd expect not to be charged the APD on separate bookings that effectively create a "connecting flight" situation.

Whether TK was correct or not, I am not sure, however. I collected my bags at IST as I had a long connection there anyway, so I did not pay the long haul APD.

Re no APD on separate tickets on UK transit - how would you police so that people don't just claim a spurious cancellable inbound booking on a different carrier, Eurostar etc.? To cover this potential evasion, it would have to be an after the event refund from the outbound carrier, rather time consuming to administer. I doubt that the outbound airline would wish to be involved, especially if it wasn't their flight inbound. Even presenting an inbound boarding card would require further research to establish UK scheduled arrival time as being within 24 hrs.

In any event, the 24hr limit ties in neatly with BA's stopover/connection limit on discounted through fares ex Europe and elsewhere, so for many I suspect it's not an issue.

not only that of BA but also the industry standard.