Could someone please explain the following. Last week we flew EDI to AUH via DOH. On arrival last week from Edinburgh we had to go through security and immigration. On the return today at Doha we were straight in the main airport and did not have to go through security and immigration (actually a blessing as our first flight was late and we had a very tight connection).

This has happened before in transferring through London, Amsterdam and Frankfurt and usually on the return journey.

I have googled this but cannot find the answer.

Thanks