date upon which the standard charges were fixed in the first instance, the tribunal shall, unless they are of opinion that owing to change in circumstances the excess is not likely to continue, modify all or any of the standard charges and make a corresponding' general modification of the exceptional charges of the company so as to effect a reduction of the net revenue of the company in subsequent years to an extent equivalent to eighty per cent of such excess:
Provided that the tribunal in making such modifications as aforesaid as respects one amalgamated company shall, so far as practicable, avoid making such modifications as would be likely to affect prejudicially the financial position of any other railway company.
(4) If on any such review the rates tribunal find that the net revenue or the average annual net revenue obtained by the company during the period on the experience of which the review is based is less than the standard revenue of the company, with such allowance (if any) as appears to the tribunal necessary to remunerate- adequately any additional capital which may have been raised or provided in respect of expenditure on capital account incurred since the date upon which the standard charges were fixed in the first instance, and that the deficiency is not due to lack of efficiency or economy in the management, the tribunal shall, unless in their opinion owing to change of 'circumstances the deficiency is not likely to continue, make such modifications in all or any of the standard charges and such a corresponding general modification of the exceptional charges of the company as they may think necessary to enable the company to earn the standard revenue with such allowance (if any) as aforesaid.
(5) Whenever on any such review such an excess as aforesaid is found, then, for the purposes of subsequent reviews, subsection (3) of this section shall have effect as if for the standard revenue there were substituted a sum (hereinafter referred to as the " increased standard ") equal to the standard revenue with the addition of twenty per cent. of such excess, and whenever on any such subsequent review an excess is found above the increased standard together with the allowance (if any) for additional capital,. then, for the purpose of subsequent reviews, the increased standard shall be increased by a sum equal to twenty per cent. of such excess, and so on:
