The following shows the 451 mirror but the same procedure applies for other variants.
Tilt the glass in towards the car and get your fingers behind it.
Reach as far behind as you can to reduce the leverage on the mirror.
Pull and the clips should disengage and the mirror will pop off.
If you have heated mirrors you will have to disconnect the 2 connections for the element.
Refitting is simple, offer up the glass and firmly push in the middle with the palm of your hand.
You should feel the clips engage, push all around to make sure it is secure.
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