"As we have explained, we do not anticipate that counsel for the Crown will have said or done anything which may indicate or convey support for or approval of the sentence indication. If however he has done so, the question whether the sentence should nevertheless be referred to this Court as unduly lenient, and the decision of the Court whether to interfere with and increase it, will be examined on a case by case basis, in the light of everything said and done by counsel for the Crown."