All opposition parties claim to be the best prepared ever for government, and all discover that the realities of power force changes in office. As Margaret Thatcher wrote about taking over in 1979: “No amount of advance preparation could change the unpleasant facts of finance or the budget arithmetic”.

The present Tory Opposition is preparing assiduously, with an implementation team headed by Francis Maude. Former ministers and civil servants have supplied advice, while briefing sessions have been organised for the Conservatives by the Institute for Government, an independent charity concerned with improving the effectiveness of administration.

Formal contacts also began in January between Shadow spokesmen and permanent secretaries, under the longstanding convention permitting private discussions within 18 months of a general election.

Much of this is about working the levers of power, as opposed to policy priorities. But there are limits to what can be achieved in opposition. The focus is all on winning. Moreover, after a long period in opposition, as with Labour in 1997, most of the Tory Shadow team have no experience of life as ministers. This is a hard gap to bridge before moving into office.

In the past the handover from one party to another has usually gone smoothly, and manifesto pledges have quickly been enacted. Sometimes retrospect suggests that it has happened too quickly, with practical problems ignored in the early euphoria. This was true in 1970: the Heath team had been seen as a government-in-exile, with plenty of detailed policies, but had left many big issues undiscussed.

Then, as later, the main problems were economic. For all its success in implementing its 1970 election manifesto, and entry into the Common Market, the Heath Government was derailed by the challenges of rising inflation and higher unemployment, for which it was unprepared.

A decade later the Thatcher team conducted a detailed public expenditure review, co-ordinated by Sir Adam Ridley, so that each new minister arrived in office in May 1979 with papers on possible cuts.

This stood the new Government in good stead as Sir Geoffrey Howe, the Chancellor, immediately undertook a big shift from direct to indirect taxes and started to cut spending plans. Nevertheless, this was not nearly enough because of the deterioration in public finances, and more tax and spending measures had to be taken, especially in the drastic 1981 Budget.

In the face of far worse public borrowing figures, the current Tory team wants to start off being even tougher on spending than the Thatcher Government was. Hence, George Osborne’s announcement that the full Cabinet — rather than, as now, a smaller “Star Chamber” group of senior ministers — would be involved in deciding the overall scale of cutbacks and in resolving disputes between departments and the Treasury.

Just like the Thatcher team 30 years ago, David Cameron has to decide how much to tell the voters before the election. Yet he knows that even the best prepared plans will look different in the harsh reality of office.

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