Sub rule l of that Rule reads thus: "20A. (13 Persons, who, not being servants of the Government, are called as witnesses in a departmental inquiry either by the authority conducting the inquiry or on behalf of the government servant whose conduct is under inquiry, shall receive the same travelling allowance and diet money as are admissible to non official witnesses summoned in criminal cases, provided that in the case of such persons who are called on behalf of the government servant whose conduct is under inquiry, the payment of travelling allowance and diet money shall be subject to the following principles: (a) travelling allowances may be Paid to witnesses summoned in the event of the government servant concerned clearing himself; (b) such allowances will be paid only in respect of witnesses whose evidence is considered of material value by the authority conducting the inquiry; and (c) in exceptional cases the authority conducting the & inquiry may, on grounds to be recorded, recommend to the Government that the principles laid down above be departed from owing to special reasons.