It’s strange that more people aren’t making Lord Heseltine’s point: that the next election is very likely to produce a hung parliament. David Cameron is far from certain of being prime minister after the next election and even less likely to have the kind of majority Labour enjoyed post-1997.

As Peter Oborne made clear in The Spectator after the last General Election, the main reason for this is the electoral system’s bias against the Conservatives. At the 2005 election Labour won 36 per cent of the vote to the Tories’ 33 per cent. This 3 per cent converted to 355 seats for Labour and 198 for the Conservatives — a massive 157-seat advantage for Labour.

If at the same election Michael Howard’s Tories had won 36 per cent of the vote, reducing Labour to 33 per cent, it would have made little difference to the composition of the Commons. The Tories would have gained around 45 seats or so and Labour would have sunk to around 305. Labour would still have enjoyed a 50-seat margin over the main opposition party, despite winning 3 per cent less of the national vote. In 2005 Labour voters cast 27,600 votes for each sitting MP, Tory voters 45,000.

Partly this is down to the over-representation of Scotland and Wales in the Commons. It’s also a result of the use of old census data when calculating constituency sizes. The last half-century has seen a steady stream of people leaving inner-cities for the suburbs and countryside — in other words, people leaving Labour areas for Conservative territory. But because the Boundary Commission works on data from the last census (the 2005 election relied on data from the 1991 census, whilst next year’s election will rely on the 2001 census) inner-city areas are consistently over-represented at the expense of suburban and rural areas.

This bias is amplified by the fact that Boundary Commissioners are obliged to reach their conclusions on the basis of the resident population rather than the number of voters in a constituency. Voter turnout is lower in inner-city areas than it is in Tory-voting areas, further disfavouring Conservative representation.

Add to all this the likelihood that many Eurosceptic voters will vote for UKIP or simply abstain - a factor at the last election, as this blog makes clear and likely to be even more pronounced at this election — and there’s still plenty for the Conservatives to worry about.