Can anyone advise how to release the tailgate it the usual way has failed for some reason. No internal handle on this car. Thanks

If its just stuck closed (no broken cable), drive the car onto a driveway apron at an angle.  Often the body 'twist' will release the latches.

 

Good luck!

Thanks Carbuff. Unfortunately not an option at the moment. Sitting on a ramp doing a few winter jobs. Any other ideas. I’m sure I’ll find a way

Jack or lift one rear side to achieve the twist?

 

Good luck. (You aren't lucky enough to have the boot floor off, I bet.) 🥴