Margaret Thatcher was undoubtedly a transformative prime minister. The only peacetime premiers who might be said to have had a similar lasting impact on British politics are the Victorian titans Gladstone and Disraeli, and Attlee, who led the great post-war Labour government

But whatever else might be said of Thatcher’s record one thing seems undeniable. She was not an investment prime minister. She may be credited by David Cameron for having made Britain great again following the malaise of the 1970s but she failed – and spectacularly so – to invest in Britain’s post-Thatcherite future. As capital spending plummeted, our national infrastructure was left to rot. Public services in particular were starved of resources. Most seriously her governments did little to help find future employment for those industries deemed beyond the pale of the Thatcher revolution.

But nothing better illustrates her failure to invest in Britain’s long term future than her mishandling of the giant windfall she was gifted on entering Number 10 from booming North Sea oil revenues. There is no doub that oil played a big part in bankrolling Thatcher’s agenda and in allowing Britain to address a chronic balance of payments problem that had besieged post-war government (Tony Blair said in 1987 that North Sea oil was "utterly essential to Mrs Thatcher’s electoral success"). But history should also record that Thatcher missed a trick in not diverting some of the proceeds of oil revenue into an oil fund, like Norway and others did. Instead she used the lot to support current spending, including covering the costs of large-scale industrial restructuring and funding expensive tax cuts to woo middle England. And what a lot it was. The table below shows government tax receipts from the UK Continental Shelf since 1980 where the numbers have been rebased to show receipts in real terms, expressed in 2011 pounds. In the years between 1980-81 and 1989-90, the Thatcher governments received a staggering windfall of £166bn.