I just had a luck escape. Whilst a race was in-play, I though I would just tweak an Automation. (The automation had already fired off). As it turns out the automation was the one that was currently in use, so anyway, I tweaked it and saved the automation, only for it to fire again!!!

Panic set in, but luckily for me it gained me an extra tenner.
So my new rule is check to make sure that the automation I am messing with is not currently in-play.