19. If the facilities and rights to be afforded by the promoter in respect of any alternative apparatus under paragraph 17 and the terms and conditions subject to which those facilities and rights are to be granted are, in the opinion of the arbitrator, more or less favourable on the whole to the specified undertaker than the facilities, rights, terms and conditions applying to the apparatus to be removed, the arbitrator must make such provision for the payment of compensation to or by the promoter by or to the specified undertaker in that respect as appears to the arbitrator to be reasonable having regard to all the circumstances of the case.