I was at LHR T5 and the check-in agent accepted my baggage 45 minutes before the flight departed. When I get to the security check with the automatic gate around 5/10 minutes later, I was blocked and was told to see staff. The staff called someone and told me my baggage would be offloaded, without letting me in the security area.

I was trying to explain that I can try to get to the fast track, but he says that's in vain as they blocked my access to the security area. What frustrated me is that I later found out the flight actually left the gate almost 35 minutes late after departure.

I tried to call BA/Avios as there's no ticketing service desk at LHR. What's my recourse for reimbursing the Avios.