Had to use this site's fill in the gaps thingy to understand what was going on with 16D, but then it was a major PDM. However, it only makes sense if you're up to speed with what's going on with the Observer's ownership structure, so I'm not sure it's entirely fair, ingenious as it is.
For late arrivals, see ilippu's very helpful post #9 for the online address of the puzzle. The new owners do NOT make it easy to find! (e.g. There's no point using the search function on observer.co.uk). Also, the new interface is a bit of a shambles - no anagram helper, no full list of clues, etc. And don't navigate away before completion because all the answers disappear if you do!