Stormont the epicentre of a political earthquake

The Stormont estate in east Belfast was the epicentre of a political earthquake this afternoon.

A changing of the political order.

The offices of First and Deputy First Minister are co-dependent, with equal powers and each not able to function without the other.

But the title First confers symbolic seniority in the pecking order, and Northern Ireland is a place where symbolism is crucial.

When Northern Ireland was created in 1921 its founders were confident they had secured a built-in permanent Protestant and unionist majority.

"A Protestant Parliament and a Protestant state" is how former Northern Ireland prime minister James Craig put it in 1934.

In the decades since, all 11 heads of government at Stormont have been unionists and Protestants.

This afternoon, Sinn Féin's Michelle O'Neill broke that cycle when she became the first Catholic and nationalist First Minister.

Her party won the right to the position of First Minister in the last Stormont Assembly election in May 2022 when it won the most first preference votes in Northern Ireland for the first time, more than a quarter of a million.

It is difficult to overstate the symbolic and psychological significance.

Ms O'Neill has vowed to be "a First Minister for all", but there is no doubt that many unionists and loyalists will struggle to accept the new political landscape.

The DUP also broke new ground by filling the role of Deputy First Minister for the first time, something that would have been unthinkable when Ian Paisley formed the party in 1971.

More history was made after the party nominated Emma Little-Pengelly to fill the role.

The Assembly member for Lagan Valley became the first Deputy First Minister to hold the office without actually being elected to the Assembly.

She was co-opted without facing an election to replace DUP leader Jeffrey Donaldson, who was elected in the 2022 poll but then opted to remain in the House of Commons as an MP rather than take his Assembly seat.

There will be much focus on how this new political dynamic plays out.

Unionists will seek to hold Ms O'Neill to her often-stated pledge to be "a First Minister for all".

With an eye on the next General Election in the Republic, Sinn Féin will seek to demonstrate that it is a party fit to lead government and prove its detractors wrong.

The seismic shockwaves may take some time to settle.