Maria McIlgorm made the comments in a letter to staff as an array of different unions walk off the job today in a mass protest over pay – affecting almost every part of Northern Irish public life: transport, hospitals, schools, and possibly even the police.

A statement from temporary Assistant Chief Constable Melanie Jones said that “within the police service itself, it is likely that a number of my police service colleagues will participate in [today’s] industrial action”.

She added: “During previous industrial action, we experienced slight delays in receiving non-emergency reports via 101.

“We will monitor this throughout the day but I want to remind everyone they can report non-emergency incidents or crimes using our online tool www.psni.police.uk/report. In the event of an emergency please always dial 999.”

The number of people on strike is estimated to be roughly 170,000.

To put that in context, that is about 8.5% of the entire Northern Irish population.

To put it another way, since the number of people working in Northern Ireland is roughly 880,000, the strikers account for roughly one-fifth of the working population.

Meanwhile, the Department of Infrastructure has said the only roads which will have gritting will be the M1 and M2 motorways, the A1 and the A4 – and even then it will be “limited”, so “extreme caution will be required for anyone travelling on any part of the road network”.

Gritting lorry driver will, in fact, be on strike not just today, but for a week.

There will be rallies at Belfast City Hall (noon), Londonderry’s Guildhall (11.45am), Omagh courthouse (1pm), Enniskillen Town Hall (1pm), Cookstown’s old post office (1pm), Magherafelt Diamond (11am), and Ballymena Harmony Hub bandstand (10am).

In the House of Lords Dame Arlene Foster accused the government of “blackmail” for insisting that any pay settlement must wait for Stormont.

Unions' mass day of action today means roughly 8.5% of entire Northern Irish population is out on strike

Mass strike: The up-to-date list of all the unions striking across Northern Ireland on January 18 – and how many members of each one are out

Trade unions on the march: breakdown of the 10 parades taking place on strike day across Northern Ireland - Thursday January 18