Westminster politics is moving into uncharted territory. Opinion polls are predicting that the Scottish National Party (SNP) may gain enough seats in the forthcoming general election to hold the balance of power in a House of Commons where, the polls predict, no party may have a majority. In those circumstances, the SNP leader Nicola Sturgeon said on television this week, the party would use its parliamentary strength to prevent the Conservatives forming the next Government and help Ed Miliband become prime minister. SNP and Labour have both ruled out a formal coalition, and a minority Labour Government would have to persuade a majority of MPs to back it on each issue. The SNP will be tempted to use its influence to weaken the unity of the United Kingdom, as part of its aim of achieving S