By Andy Silvester The Treasury raked in an extra £1.4bn in revenue as a result of freezing excise duty on Scotch and spirits for five years – with the economic boost generated more than making up for the lack of immediate tax revenue – according to the latest data. Excise duty on spirits was kept steady, not moving for inflation, for the five years until last year. In each year the Treasury in fact received more revenue than it had forecast if the duty rate had gone up by inflation. For instance, the official budget watchdog the Office for Budget Responsibility forecast revenue from spirits du…