• Please don't twist it!

    there is a tool thats perfect for old seat posts (unless they have chemically welded in which case your buggered, but doesn't look like that here) its just a single ended hand saw that takes hacksaw blades. Fit a fresh metal blade and away you go.
    Make at least 2, maybe 3 cuts, and eventually you will get through to the seat tube (its obvious once you've gone through the alu). Make a large pot of tea, stick an old matt out and get to it on the sofa, should take 45-90minutes max.

    I solved a few few times with a adjustable reamer.
    Takes some time, but works perfectly.
    A good bike mechanic or race dealer has a set.
    And on Ebay, these are also not that expensive.

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