President Vladimir Putin has insisted during the crisis over Ukraine that Nato should stop its encroachment towards Russia’s borders. But his demand is having unintended consequences in Europe’s far north, reviving talk of whether Finland and Sweden should join the military alliance.

As the world’s attention focuses on the Russian troops massing on Ukraine’s border, leaders from across the political spectrum in both Nordic countries have stressed that they have the option to apply for membership at any time.

“The debate is vivid and unprecedented. A lot is going on. A lot depends on what happens next,” said Henri Vanhanen, foreign policy and EU adviser to the centre-right National Coalition party, Finland’s main opposition group and a proponent of Nato membership.