For Scotland the key number in the political pantheon is “45”. The SNP won 45 per cent of the constituency vote in the 2011 elections and 45 per cent in last September’s independence referendum. The key to deliver more seats will be for First Minister Nicola Sturgeon to convince some of those who voted “No” and are concerned about a potential second referendum to put their cross in the SNP box. The challenge is now no longer between Left and Right, but between those who voted “Yes” and “No” in the referendum. A novel aspect of this election is that for the first time Holyrood parties will have to set out revenue-raising and spending plans. Scottish Secretary David Mundell MP hopes to put the laws handing over full control of Scottish earned income tax to Holyrood into action in 2017, rather than 2018. Scottish politicians will be responsible for setting taxes to raise about a quarter (about £10.6 billion) of what they spend (£43bn). The Scottish Conservatives have become devoted tax devolution enthusiasts, now that the traditional Tory offering of cutting taxes is open to them. The other parties will also have to come forward with their own fiscal proposals. That said, there is little chance of the Tories being close to power in Holyrood, although they may gain seats. Labour, under Corbyn, is still in total disarray. An SNP victory at Holyrood might be on the cards, but the timing of EU referendum is uncertain. Don’t be surprised if David Cameron calls the vote next year rather than in 2017. l Alex Orr is MD of Orbit Communications