Viaro Energy Strategy, page-59

The removal of investment allowances reduces the tax relief to about 84% down from 91% if my calculations are correct. The Capital allowance claims that can be taken into account in calculating EPL protits will be reduced; however the extent of the reduction will only be announced in the October Budget following engagement with stakeholders. That could be as much as 100% or 1%. We don’t know. The net effect is that total relief could be as low as 46% or as high as 84%. My guess is that they will look to mirror the Norway model of 78% relief against a total tax of 78%.
But as Mitchdon has suggested, the sale of shell’s assets to Viaro, if it happens, will definitely turn the dial . More waiting…