Originally Posted by mjh0

Normally, when you connect with a fairly normal 2 hour connect time, the containers for the next flight are already being made up in the baggage cellar - there will be an assigned position for the bags to be delivered to.

When you are making a longer connection, your bags need to go into a holding pen until it's time for your flight to be made up.

As I recall at LHR T5 this is done using a robotic automated "warehouse" in the catacombs which knows where each stored bag is and what flight it's for.