 However, this began to cause increasing problems.Firstly, clubs often had difficulty agreeing dates, and the tournament struggled to finish on time - for example, the 1964–65 final was not played until early June, over a year after the group games had started; and in 1963–64 and 1965–66 it was concluded in late May.The second reason was the insistence of UEFA that any clubs taking part in the European Cup or UEFA Cup Winners' Cup could not continue games in other European competitions after the end of the summer break.