To do this turn the seat upside down and ensure that it is steady.
The bottom of the stem will be visible, with a metal rim. Firmly strike the metal rim with a mallet until the base seperates from the stem. If your seat is quite old the stem will be firmly attached to the base and so may require a number of strikes.
Watch this video, for more information on how the stem can be detached from the base (and saddle).
If you have difficulties fitting your arm rest, please call us on 020 8532 5100.