I am looking at GOT-LHR-SFO-LHR-GOT. I would like to do the final LHR-GOT segment but .....

.. if the inbound from SFO is late and I miss the last BA flight of the day to GOT (and consequently my same plane return to LHR) what happens? There is a direct SAS flight that leaves a couple of hours later. Would they try and book me on that? Or would I have to wait for a BA flight the next day? I'd have missed my return whatever happened but would hope for clemency if I was getting a later BA flight.

I suspect, in practice, I'd go off in a sulk and get the bus home but am hoping someone might be able to tell me about options.

Thanks.