sentences:  The tax was calculated by means of a 9 times P/E ratio, whereby the average post-tax profit in the four years after privatization was multiplied by 9 to give the value for the purposes of the tax.The difference between this value and the total market capitalisation based on the company's flotation price was subject to a 23% "windfall tax".The tax was charged to the company and was payable in two instalments on 1 December 1997 and 1 December 1998.