LHR-JER? We have plenty of gate availability after BE’s demise.
Whether it would ever prove profitable is a different question. It was tried before by BMI. I doubt BA could fill an A319 on a daily basis - do they have anything smaller and spare? Or might they lease something suitable? And yet there must be a tourist market from the west of London?
An early and late rotation to connect to TATL? Do we really need 5-a-day to LGW? One can dream.