Restrictive Relative or Non-restrictive Clause?

Even though I've been learning English for many years, I can't tell immediately whether I should use restrictive or non-strictive clause when I read a sentence in which a relative pronoun is used.   I just read a sentence, and I thought a restrictive usage of the relative pronoun should be used, but I was wrong. Two native English speakers corrected the entry, but neither of them corrected the part.  Could someone explain it why it's written with the non-restrictive clause?  "He shared his speech on X, which he delivered at Shinbashi station." Thank you for your help.