witness shall be tendered to such witness upon service of the subpoena, failing which no subpoena shall issue. If upon service of the subpoena all expenses due to such witness have not been paid the subpoena shall have no force and effect. (4) In the taxation of costs between party and party, no amount shall be allowed for any witness whether for attendance or travelling expenses unless there is produced to the Taxing Officer proof that such amount has already been paid or tendered to or claimed by such witness. (5) In the taxation of costs between party and party, nothing shall be allowed for any witness not examined unless upon proof that his evidence might reasonably have been believed to be material and necessary. (6) If the number of witnesses summoned, or if the number of affidavits filed, is manifestly greater than is reasonably necessary, there shall only be allowed against the other party the charges for such witnesses or affidavits as were reasonably necessary. (7) In the taxation of costs between party and party, no amount shall be allowed for any witness in respect of personal attendance or travelling expenses if the fact or facts which such witness is subpoenaed to prove have, before the issue of such subpoena, been admitted to the party taking out the subpoena by the opposite party: Provided that such admission shall be in writing, signed by the party making it or his legal practitioner acting on his behalf. (8) When the same person is a witness in more cases than one heard on the same day, he shall be entitled to no more than one fee for personal attendance and one allowance for travelling expenses, which shall be equally divided between such cases. 20. (1) In all cases where a notice of taxation is necessary, seven days' Taxation of notice together with a copy of the bill of costs shall be given by the legal costs practitioner on behalf of the party whose costs are to be taxed to the other party or to the legal practitioner of such other party.