Keeping Property Separate, does not Always Prevent a Property Settlement

Separation of property and finances during a relationship will add strong weight to an argument that there should be no alteration of interest in property, but will it stop a property settlement?
Do I need a Financial Agreement or Consent Orders?

We have acted for many clients who are (unsurprisingly) shocked and horrified at having been served with an application from their ex-partner with whom they separated over 10 years ago.