5. Except in so far as in any particular case any immunity is waived by the tribunal, persons participating in proceedings shall have:—
(a)in respect of words spoken or written and documents or other evidence submitted by them before or to a tribunal to which this Order applies (but not where such words, documents or evidence or any part thereof are communicated by them or on their behalf outside the tribunal), the like immunity from suit and legal process as is accorded to the head of a diplomatic mission;
(b)while passing in transit through the United Kingdom during their journeys to and from the proceedings or while in the United Kingdom for the purpose of such proceedings there, immunity from criminal proceedings and, except for the purpose of detaining a person who has escaped from legal custody, from personal arrest in respect of acts or convictions prior to the commencement of the journey, provided that their presence at the proceedings has been authorised in advance by the tribunal and that fifteen days have not elapsed from the date when their presence is no longer required by the tribunal.