H 23An assisted passage or the savings between the actual cost of a passage and the maximum of a public servant's entitlement shall only be paid where those in respect of whom he is granted such passage accompany the public servant on his outward journey or join him in three months of his departure and subject to rule H22 above the same principle shall apply mutatis mutandis to the return journey provided that these requirements may be waived by the Permanent Secretary , Public Service Ministry , if he is satisfied that it is necessary , on medical grounds , for a public servant or his wife or child to seek medical treatment abroad .