If a pax misses conformance at front of house then the bags are turned red and sent straight to the arrivals hall. We don't put people in the stocks if they miss conformance, we just change their tickets as per the rules.

A pax who is late at the gate however will be made to walk over hot coals before they can travel on BA again.

TBH it would be a lot less hassle if the OP leaves the bag at left luggage and checks it in when he knows he is travelling. If the flight is missed, he'll need to be escorted in to the baggage hall to get the bags.