@Ruthrobin, yes, I assumed that was the reason for the generosity, especially as the last Listener of the year, but I spent about a week more on 4326 than I usually do and it would have been nice to feel that I had arrived at the correct solution through sheer intellectual brilliance. I've been doing the Listener since the mid-1960s, and I thought I knew what 'Lengths in brackets refer to grid entries' meant, but like olichant I wondered whether this phrase had some special meaning that had hitherto eluded me. I'm still puzzled, that's why I'd like to know what Sabre's thinking was. I took my final decision from 'Before entry into the grid, each clued answer...'
@s_pugh, my last clue solved was also the 3rd jumbly, which was all the more ridiculous as I had already paired up the unjumbled word with its unclued entry.