In a few days, I will be travelling from Bangalore, India to Berlin, Germany via New Delhi and London, i.e.:
The entire journey is booked on one PNR and ticket.
As per the Air India website, the Indian customs and immigration formalities will be handled in BLR so that in Delhi, I will technically be performing an international transit.
My question, however, relates to the transit in LHR. Will Air India be able to check my baggage through all the way to TXL? Additionally, will Air India be able to issue a boarding pass for the last (BA) segment of my journey?
Possibly related: In my understanding, the transfer in LHR should again be international, i.e., no customs or immigration. According to the LHR connection planner, this understanding seems to be generally correct (no mentioning of passing through immigration) even though I will arrive at Terminal 2, while my onward flight to TXL leaves from Terminal 5. It does however say
You will pass through security screening at this point. If you are a non-UK resident and have goods to declare to HM Customs, please use the Customs telephone before security control.
Why would I need to declare anything to UK Customs when I'm not even (technically) entering the country?