Oh the difficulties of maintaining back story!
And yes I know it's something many writers abhor, and that an anxiety to do so is seen as amateurish, so although I have put in several thousand words of it, I am now trying to stamp it out. Drip feed the minimum, as and where necessary and/or applicable.
I had originally dealt with it by writing a dramatic first chapter and followed it with a catch-up second, but no matter how imaginatively I tweaked it, there were dangerous heavy undertones which threatened to drag the as-yet-uncommitted reader into the morass.
And so I am trying to combine (aka 'divide and rule) the two chapters while cutting ruthlessly. Which has brought me to use Tracking seriously for the first time ever. Another learning curve.