Dual Flush Toilet Cistern - How do you remove the cistern lid?

The two part button is located in the centre of the cistern lid. When I try to lift off the cistern lid the edges are free but it is being held in the centre, presumably by some form of connector to the two part button and I don't wont to force it. Any ideas how I can get the cistern lid off?

Okay folks I have found the answer.

The dual flush buttons on the top are in an outer ring. The outer ring needs to be unscrewed to allow the top to come of. It may be difficult to get a grip on the outer ring if it is shiney, best to put some rubber gloves on, press down on the ring and turn at the same time.

However, be aware that other types have a single screw in the fitting accessed by removing the buttons - press down 1 button and gently remove the other button then remove 1st button look inside and there’s your screw.