OK now, I've just done a 'non destructive' system restore using my recovery disk and it seems to have done the trick.
I didn't realise one could recover without losing any data but with Advent, you can, it seems.
OnePlus 5 review
Alice Saey's mesmerising animation for Dutch singer Mark Lotterman
iPad Pro 10.5in (2017) review
Comment booster votre iPhone ?