Demand possibly, but not enough space on the Brighton Mainline, which is very, very crowded. Any such train would end up being stuck behind a train stopping at Clapham, E Croydon and Gatwick, similar to how the Gatwick Express doesn't go any faster from Victoria to Gatwick than a train that stops at Clapham and E Croydon.Obviously not the train, but the idea of a non-stop service between London and Brighton. Surely there must be enough demand for this?
I see where you're coming from, but that will immediately lead to complaints that either a) the train is too slow (from those on it) or b) if it's going slow through 'my' station why not make the extra stop so 'I' can get on (from those not on it).It could go without stop, slowing down if necessary, there would be something agreeable and exclusive about that, no disturbance caused by passengers joining and alighting