ERM had been haunted by repeated devaluations and exchange rate crises, the most notorious episode occurring in 1992/1993.
In the absence of EMU, the 2007/2008 financial crisis would have brought such a system under severe pressure, as doubts about the liquidity and solvency of specific banks would have combined with a drying up of funding in the interbank and foreign exchange markets, concerns about government budgets and doubts about the willingness to defend fixed exchange rates in particular if this meant raising official interest rates in the face of economic slowdown.