An equitable solution?

Fuel prices - the Government say that reducing or foregoing a rise in fuel duty is not on because it would cost too much. But surely when they originally did their sums they couldn't have factored in the steep rise in the cost of oil as a result of the shenanigans in the Middle East, so there must be a windfall element in the tax they are getting on fuel at the moment.  Wouldn't it be fair to give that back to the motorist?