Handbrake failed.
Had car as hire car from AVIS - appeared to be in good condition.
With the handbrake on, the car rolled 50 metres across a main road and fortunately missed all traffic/pedestrians.
Looking on google; Vauxhalls appear to have handbrake problems - how many others have experienced similar?
Car performs well, is comfortable and would make a good family car - the handbrake issue is very alarming though.
If your Zafira is Auto, why not just put it in park and not use the handbrake? I never use mine on my Lexus.