Remove the cabinet from the wall and lay it on its back on a table or worktop*. You may want to cover the table or worktop with a towel or something else protective.
Use a wire ie. guitar string or similar wire or a putty knife or similar to cut through the adhesive tape holding the mirror panel to the carcass of the cabinet
Place the wire between the cabinet and the side panel and pull it through to cut the adhesive tape that is holding the mirror in place. There are usually 2 lines of tape running top to bottom.
Do not attempt to pull the panel away from the carcass until all the tape has been cut through. The mirror will break and could cause serious injury
*if the cabinet has lights or a shaver socket you will need to disconnect it from the electrical feed. This should be carried out by a qualified tradesman
