Ill give you my frame of reference trough refering to the emergence of the Flemish parliament in Belgium and the consequence for the state.
From 1830 until 1970 Belgium was a unitary state with a single government and a bicameral national parliament. The laws issued by Parliament applied to all Belgians, and government ministers exercised their authority across the length and breadth of the country. Between 1970 and 2001 the Belgian Parliament approved five successive constitutional reforms. Slowly they changed Belgium from a unitary into a federal state. Part of this was to give the communities and later the regions, their own parliaments.
On December 7, 1971, the Cultural Council for the Dutch-speaking Cultural Community held its first meeting, later followed a parliament for the Flemish Region. Flanders decided as early as 1980 to merge the Flemish Community with the Flemish Region. As a result, Flanders now has a single parliament and a single government with competence over community as well as over regional matters. This Parliament was called the Vlaamse Raad until it was officially renamed Vlaams Parlement (Flemish Parliament) on June 13, 1995. Over the last thirty years, Flanders has thus developed into a separate state within the federalised Belgium.
From my perception, the emergence of a regional goverment is (or can easily be) a (potentially big) step towards that region becoming a state within a federation of states.
If the UK is not really what its name suggest but whatever the political reality is, then 1997 is a very significant date in regards to what the UK is nowadays imho.