The original stimuli for the Maastricht Treaty were economic. By the late 1980s the Exchange Rate Mechanism – the system introduced to stabilise European currency exchange rates against each other - had become a system worth defending.
But France and Italy argued that reform was necessary in order to tackle their disadvantages relative to the German Deutsch Mark. Meanwhile in the UK, the Chancellor, Nigel Lawson, was struggling with Prime Minister Margaret Thatcher over whether sterling should even join the ERM.
Thatcher had mistakenly assumed that early moves towards closer economic integration would be blocked or diluted by either the Bank of England or the Bundesbank. But in the event, the Delors Committee backed the initiatives unanimously, establishing the blueprint that would ultimately lead to the euro.
Later British alternatives for a parallel currency and a 'Hard ECU' were never more than temporary distractions that only served to indicate how distant the UK Government was from wider moves towards monetary union.
By the time of the crucial inter-governmental conference in December 1990, Thatcher had been forced out of office and her successor John Major was fighting a losing battle.
The momentum towards the Maastricht Treaty was broadened and strengthened by the dramatic events in central and eastern Europe in late 1989 and 1990, with the collapse of the Berlin Wall prompting a parallel conference on political union.
The dominant mode of decision-making in these policy areas was to be inter-governmental, respecting unanimity and national differences. But while the texts inserted into the Maastricht Treaty had a rather grand tone, the reality was far more modest.
These unrealised ambitions were only really taken up again at the convention to establish a European Constitution many years later.
The Maastricht Treaty had several legacies which, combined, have questioned the case for European integration and the legitimacy of the course taken in that direction.
The most tangible consequence, by far, has been the establishment of the single currency which has transformed the economic landscape. The other policy commitments - a common foreign and security policy and new competences on justice and home affairs - have had less substantial outcomes.
The Iraq War shattered any pretensions of a 'common' European stance. A second consequence concerns Britain. Maastricht revealed the deep tensions within the Conservative Party over British participation in the EU: divisions that have been masked, but not overcome, in recent years.
These served to create doubts as to whether Her Majesty's Opposition was electable or not - an exceptional affliction for the Tory tradition. Maastricht was the basis on which 'eurosceptic' MPs identified themselves - hitherto their numbers and influence had been fewer - and it also established a long-term pattern of press hostility.
A third consequence was a new agenda of European integration with member states moving ahead at different speeds and a new set of issues concerned with managing the relationship between an inner core and an outer periphery.
With its opt-out on the euro, the UK Treasury was made aware of such issues, but similar problems have arisen more generally over foreign policy and justice and home affairs.
A fourth consequence has been the perception - shared by pro- and anti-EU leaders - that the integration process has stretched too far ahead of public opinion.
The backlash against the Maastricht Treaty in Britain, Denmark and France gave it the aura of an elitist indulgence. And, as seen more recently with the Constitutional Treaty, the issue remains of how to reconcile major new steps in EU policy with the legitimacy that can only come from public engagement.
Maastricht questioned, as never before, the relevance and purpose of the Union -- but the answers have proved elusive.