Long story short. I staged at idle instead of having the brakes on and the tranny loaded at 2000 rpm. Dont ask why ??
So she moved bit when i floored it but she backfired and I came off and then went back on hard on the pedal.
To say the MG was unsettled is an understatement.
The Slo mo vid shows all

https://www.youtube.com/watch?v=wJw3Be2xpVs