Just a little story.
I realised that cracking the two 12 letter and two 11 letter clues was key to filling in the grid.
The first one I spent time on was “Borderline acceptable . . . “ which seemed pretty obviously to involve an anagram. My solution was NOT BORN HERE, with A as the surplus letter. (Yes, I eventually realised there was only one R to play with – but not until much later.)
I thought this was perhaps an old snobby/racist expression re ‘acceptability’ that I’d never come across.
Whatever. I then decided that the right hand column looked the most likely place for it, and duly entered it. This helped me solve the entry for the top row - and so go on to fill almost all the grid before twigging that there had to be something wrong.
So, massive error. But made hardly any difference.