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The arithmetic already takes into account a series of SNP controversies over independence strategy, gender self-identification, a police investigation into party finances, leadership changes and the collapse of a power-sharing deal with the Greens.

"It depends on the arithmetic," he said, suggesting it could be discussed if there are "two parties thoroughly at the same kind of level".

Merz chose to push the changes through the old parliament, knowing the vote arithmetic was more favourable now than it would be after 25 March, when the new parliament session begins.

It is painful and it is awful and it is crude, but this is also the grim arithmetic by which big wars are won.

Once English and maths, or at least arithmetic, were effectively compulsory for students in S4.