What is the definition of successfully conquered? If a country has been conquered in the past but is now independent is that not unsuccessfully conquered, only successfully conquered if it becomes fully integrated until such time as it becomes independent? So Scotland is still ‘successfully’ conquered despite the wishes of many, but England is not?
personally id argue the formation of the UK was not because Scotland was conquered, but for other reasons, hence it becoming a treaty of "equal" and not (at least in writing) with one in control of the others land.