Adding additional checked baggage in transit
 

I'm flying HAN -> HKG -> LHR, with half a day in HK. I want to check a small bag in at Hanoi all the way to London then check in a large bag at HK Central and then a small bag at the airport (HKG).

Is this possible?
Also, how do they work out the combined weight of your total baggage (can they)?

Thanks a lot!

Yes, you can do this. Depending on if the carriers are the same for both sectors, they may or may not know the combined weight of the bags. The best would be to avoid going over the combined limit.

I've done this before, but both legs were with CX. Just show them your onward BP, check-in agent will then take care of the rest.

Airline should know exactly how much of weight you check-in, as one of the compensation criteria is base on weight if they lost your baggage. But I've got no idea if this information would be share by 2 airline companies on the same ticket maybe someone can shed some light on this?

I've checked in two bags, and then checked in two more in a transit, expecting to pay for the two bags, only to be treated as if I only had these two bags.

But perhaps it was different since I was on two different tickets (AA to CX).