Depress one of the flush buttons, carefully lever the other one out with a screwdriver (You will see a small slot in the button). Remove the first button to reveal the holding screw.
Simon Jeffery, December 2008
you turn the plastic button on the top of the loo that is used to flush it and pull and it will come apart. it is held on by two clips
warren, November 2008
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how to remove the lid from a Roca dual flush cistern?