I'm on a Circle line train going anti-clockwise from Tower Hill to
King's Cross. The train pulls into Aldgate and proceeds to sit there
for several minutes. A Metropolitan line train sits in the adjacent
platform, with people sitting on it waiting to depart.

Sometimes the Circle line departs first, but quite often the
Metropolitan line train leaves first instead, which is annoying when
I'm rushing for a connection at KX.

Is there any way to tell which train is going to depart first? What
happens at the moment is that people hang around half way between the
two, hoping to run to whichever train sounds its "doors closing" beeps
first. And often not getting there in time.

I suppose my best bet is to watch the signals and see which one goes
green first, but you can't see both sets at the same time except when
standing at the very front. And I get the impression that the driver
starts closing the doors before the signals change. Are there any
other lights or clues I could be watching out for?

PaulO