Cracking and flaking is a bond failure, mate. The paint film either couldn't grip the surface underneath or it dried wrong. It's rarely the paint's fault — it's nearly always the prep.
The usual culprits:
Painting over the wrong surface. Water-based emulsion over old oil-based gloss or a chalky, distempered wall has nothing to key into. It dries, shrinks slightly, and lifts. Same story with greasy kitchen walls or dusty new plaster — the film sits on top rather than soaking in.
Skipping the primer. New plaster needs a mist coat (emulsion thinned roughly 30% with water) to seal it. Bare wood, MDF and patched repairs need a proper primer. For anything dodgy — old gloss, stains, glossy melamine — Zinsser BIN or Cover Stain gives you a bombproof grip coat. Skip this and you're gambling.
Crazing and alligatoring. Fine cracks across the surface usually mean a topcoat was applied over an undercoat that hadn't fully cured, or thick coats were piled on too fast. Each layer dries at a different rate and tears the surface.
Damp. If water's getting behind the film — penetrating damp, condensation, a leak — it'll push the paint off no matter how good your prep was. Sort the moisture first.
To fix it: scrape back all the loose, flaking material to a sound edge. Sand the edges feathered. Wash off any grease or chalk. Prime bare or suspect areas. Then repaint with the right system top to bottom — don't mix solvent and water-based without a bridging primer.
For a hard-wearing wall finish that holds up, Little Greene Intelligent Matt or Dulux trade emulsion are forgiving and durable. On woodwork prone to cracking, a flexible primer plus Farrow & Ball or Crown eggshell beats brittle old gloss.
No amount of premium paint saves bad prep. Spend your time on the surface — that's where the job is won.