Advice on prepping/painting over interior mould/damp

[Dee]

I need advice on how to proceed with decorating over old mould/damp.

Wiping my hand over the patches and it's dry and powdery.

The damp was primarily caused by ivy, blocked gutters and lack of ventilation by my tenants. 

I don't want to do a bodge job but not sure how to treat either. 

Thanks

Edited 2 hours ago by Dee

[nod]

Scrape and clean thoroughly 

Bleach Leave to dry 

Then use a cheap oil based undercoat to block staining