Originally Posted by eric_packer
My experience with onward domestic UK connections via London is limited to Glasgow and Edinburgh. With that disclaimer-
As number_6 says, you will clear Immigration at LGW but won't need to claim and recheck your baggage there.
In Edinburgh, bags that had originated overseas were separated from domestic baggage and diverted to a dedicated "international" carousel. In several journeys, however, I never saw an actual HM Customs officer on duty. I think there may have been a telephone with which passengers were meant to declare dutiable goods on the hono[u]r system. I never saw anyone doing so.
Just because you didnt see them it doesnt mean they are not there.
Try looking for the 2 way mirrors/screens. The level of coverage depends on where the flights are coming in from.
I am always amazed how they seem to come from nowhere to catch the real criminals, not those carrying an extra bottle of drink.