Whatever the date (I'm pretty sure Peggy has the date wrong) - it was never a 'rule' that people should sing only from their own traditions (any more than it was practice to 'audition' visiting singers from the floor, ashas been suggested) - it was policy for the Singers club residents only (how could it be anything else - Ewan was never in a position to make 'rules' for any club even if he had wanted to).
In the end, the proof of the pudding....... as they say.
It was this policy, in the Singers Club and elsewhere, that threw open the English, Scots and Irish repertoires, for which I, for one, will be eternally grateful.
Jim Carroll