Somewhere on this forum it was determined you cannot extract a tap washer through a tap extension. I can't locate the thread now, but I think I was a non-believer at first until I tried it myself - I think I even provided a photo?
Sadly, I forget all about this yesterday. I could remove the spindle - but not the washer. Then I realised was I looking at the brass extension surface - not the background piping.
Took a while to figure out how to remove the extension. I started to panic as I didn't have a large enough metric socket but a perfect fit was achieved with a 1-1/8" socket.
Would Locktite of sorts solve this from happening again?
Cheers.