I have no idea if anyone has come up with this before or not. I just kept playing around with it until I came up with what worked for me.
Casting on stitch:
This can be done with the usual chain stitch or by this method I worked out which gives a nice finish and better stretchability.
Crochet 2 chains. Hook through 1st chain and pick up and bring back yarn, then yarn round again and back through both stitches on hook.
Repeat ensuring that this time the hook goes through two parts of the stitch, bringing yarn back through, then round again and back through both stitches on hook.