In a case where a complaint became visibly distressed during giving evidence and a Judge intervened the Court gave guidance as to the correct approach :
First, in our view the recorder was wrong to characterise the questions being asked in cross-examination as being objectionable because they were ‘speculative’ or because they had not been foreshadowed in the Defence Statement. The defence case may be a denial that an event (or in this case, the offences) described by a witness took place. The defence is entitled to test the truth and accuracy of prosecution evidence by questions which test their likelihood. Cross-examination of what the recorder described as the ‘mechanics’ of the how something happened may lead a jury to conclude that it did not happen, or may not have happened, in the way described by the witness. In our judgment such a challenge does not have to be specifical- ly pre-figured in a Defence Statement provided the Defence Statement otherwise complies with s.6A of the Criminal Procedure and Investigation Act 1996.
Secondly, there are now a number of statutory provisions, Criminal Procedure Rules and Practice Directions directed to identifying vulnerable witnesses and enabling them to give the best evidence they can. It is unnecessary to set these out in detail in this judgment since they are conveniently summarised in Blackstone 2017 at 19-48 and Archbold 2017 at 8-217, see al- so Wills (Practice Note)  1 Cr App R 16.
CPD1 3D identifies people in court who may be ‘vulnerable’. These include those under the age of 18 and those with specified disabilities, but may also include others ‘who are likely to suffer fear or distress in giving evidence because of their own circumstances or those relating to the case’. CPD1 3E refers to ‘Ground Rules Hearings to plan the questioning of a Vulnerable Witness or Defendant.’
47. CPD1 3E.1 provides:The judiciary is responsible for controlling questioning. Over-rigorous or repetitive cross- examination of a child or vulnerable witness should be stopped. Intervention by the judge … is minimised if questioning, taking account of the individual’s communication needs, is discussed in advance and ground rules are agreed and adhered to.
CPD1 3E.2-6 includes detailed provisions in relation to ‘ground rules’ for (among other things) cross-examination. CPD1 3E.4 sets out:
All witnesses, including the defendant and defence witnesses, should be enabled to give the best evidence they can. In relation to young and/or vulnerable people, this may mean departing radically from traditional cross-examination. The form and extent of appropriate cross- examination will vary from case to case. For adult non-vulnerable witnesses an advocate will usually put his case so that the witness will have the opportunity of commenting upon it and/or answering it. When the witness is young or otherwise vulnerable, the court may dispense with the normal practice and impose restrictions on the advocate ‘putting his case’ where there is a risk of a young or otherwise vulnerable witness failing to understand, becoming distressed or acquiescing to leading questions. Where limitations on questioning are necessary and appro- priate, they must be clearly defined. The judge has a duty to ensure that they are complied with and should explain them to the jury and the reasons for them. If the advocate fails to comply with the limitations, the judge should give relevant directions to the jury when that occurs and prevent further questioning that does not comply with the ground rules settled upon in advance.
See also Lumemba  1 WLR 1579 - where the court made clear at :
The trial judge is responsible for controlling, questioning and ensuring that vulnerable witness
es and defendants are enabled to give the best evidence they can.
Thirdly, in addition to the provisions dealing with vulnerable witnesses, the court has the more general overriding objective of dealing with cases justly and in accordance with the prin- ciples set out in CPR Rule 1.1(2). CPR Rule 3.2 sets out how the court may achieve this by ac- tive case management; and CPR Rule 3.11(d), which deals with the conduct of a trial, includes the power to limit examination, cross-examination or re-examination of a witness.
Fourthly, the exercise of the court’s powers and the proper consideration of the advo- cate’s duties in relation to vulnerable witnesses generally presupposes that these are ad- dressed at an early stage, sometimes with professional assistance. Thus, CPR Rule 3.2(3) re- quires the court to give directions which are appropriate to the needs of the case as early
possible; and Rule 3.5 sets out the court’s case management powers, which include giving di- rections on its own initiative or an application by a party.
Fifthly the court has the power to restrain lengthy and immaterial cross-examination which has the effect of unnecessarily prolonging proceedings, see for example Simmonds and others (1967) 51 Cr App R 316, 320 and Kalia (1974) 60 Cr App R 200, 209-210, and the ref- erence to Mechanical & General Invention Co Ltd v. Austin and Austin Motor Co  AC 346, 349. In addition, advocates are under a professional duty to consider not only whether a proposed question is legally permissible but whether it is ethically justified, and should not make statements or ask questions merely to insult, humiliate or annoy a witness (see for ex- ample, The Bar Standard Board Handbook r.C7)