How to remove mould from wallpaper?

You can use a weak water and bleach mix to kill it but ultimately you need extra ventilation in the room to prevent it.

Hi. It's difficult to effect a permeanent eradication of mould in wallpaper sorry. There's a multitude of mould cleaning liquids but they all will have a bleaching effect and although they may remove the mould, the stains may remain and the spores very likely to do so, leading to further re-growth. Re-decoration and addressing of why you have a humidity/condensation issue is the permeanent fix

To me no brainer, need more ventilation, possibly dilute suger soap

Mould is a spore and unfortunately it's best to remove the wall paper back to the plaster and acid wash all the area to kill off the spore and repaint using an anti fungal paint to prevent the return of the spore and you also need to increase ventilation and ideally heat to this are as I would imagine it's cold to touch. Mould is formed by humidity in the air caused by everyday living and it's the humidity finding a few point and forming surface water to occur Also look into a positive ventilation system such as a nuaure unit these are around 300 to purchase and are great but get one with a in built heater