What was it like being the Guardian’s national news editor?” the commissioning editor asked. There are no shortage of events to reflect on after five years in the job after all. Two general elections, two referendums, a dismal string of terror attacks and the horror of the Grenfell inferno. And that’s just a start. A turbulent quinquennial for a nation that no longer knows itself, whose elites repeatedly reveal how little they understand or control. “Like swallowing a waterfall,” I replied.

A typical smart aleck answer perhaps, though aquatic metaphors often seem appropriate. News always flows, sometimes it pours, flooding the Guardian newsdesk without cease via proliferating channels. Every news editor, on arrival in the morning, organises their desktop to highlight the best of the news wires, at least two TV stations, BBC and Sky News, Twitter and other social media. Then they contend with the constant stream of email and chat messages from 50 reporters – the most committed in the business.

Sometimes, for fun, you can explain to younger colleagues how, 15 years ago, pre-internet, it was not necessary for this reporter to start writing until 4.30pm when the first edition deadline was 7pm. Five years ago, when starting on the news desk, the aim would be to publish an article within 15 minutes of a news break. Now the task is to beat the rolling news channels and publish, within moments, a single paragraph starting from the desk that is filled out, revised and updated by reporters throughout the day.

Reporters know they may be called on at a second’s notice and editors have to make decisions equally quickly. It is intense, thrilling and ultimately exhausting. The national, or home, desk covers UK news, politics, crime, human interest and social affairs. It is situated next to colleagues on foreign and opposite the web team, responsible for the front page of the site. The adjacency matters in this digital age.

By 8.45am, when the first news meeting is held, it is necessary to have an outline plan for the day. A separate print newspaper team take the best of the web and make it into the daily, and they constantly keep in touch too. There is a desk team of about eight, publishing perhaps 30 stories a day and rejecting many more. In London the first national editor arrives at 7am, the last leaves after 1am. But that is not enough: full overnight cover is provided by colleagues in Sydney, whose assistance during the terror attacks and tragic fire of the spring and early summer was invaluable.

A deadly incident can happen at any time, beginning as a wave of whispers on social media and the police knowing no more than you. Manchester and London Bridge both happened in the late evening, Grenfell later still. How serious is it? Time to open a live blog? Time to send reporters to the scene? Will they be safe? Who is on duty, who needs to be kept informed and who will you need early the next morning to find out who did it, what caused it? It all needs to be worked out in an hour or so, and as calmly as possible.

This begins to answer what news editors do. The job is to cast, clarify and communicate. Some stories are exclusives hauled in by reporters, others relate to events and developments and belong to specialists, but the rest are assigned by the desk because they don’t belong to anybody in particular. It may not be Hollywood but around half of the bylines are part selected by an editor, mindful of the talents of each reporter and, of course, who is free. Each writer needs to be given a canvas, instructions on what to aim for, what to exclude, what colleagues on related stories are doing; the line to take is agreed between the editor and writer and, where necessary, filed copy needs to be rewritten for lucidity and impact.

Editors help decide what is important too, although often it is obvious, for instance when Britain votes for Brexit and David Cameron goes. A list with the news ranked in a rough hierarchy is produced. On quieter days, as the newspaper deadline looms, the question to ask is “what is the most important thing happening in Britain today” or more precisely what will that thing be tomorrow morning. The question is a reminder of what a privilege the job is, an eyrie from which the mood of the nation can be discerned and the clockwork of its interlocking parts perceived. One can observe what Number 10 is trying to do each day, and whether they succeed or fail. Cameron and Osborne were hyperactive, prepared to govern just for the afternoon; team May’s vow-of-silence media game probably last worked in the 1950s.

Yet amid all the speed, it is necessary to think, to give reporters latitude to develop their ideas, to shed preconceived notions and establish the facts, to hunt for exclusives. This is where so much of the Guardian’s best work lies, and where the daily, weekly, monthly challenge is. Many of the most important stories come not from one big revelation but through patiently developing a theme – London property ownership, the influence of Russian bots, or sexual abuse and harassment.

The power of the Guardian is the excellence of the journalism allied to the volume of its megaphone. A brilliant exclusive about Home Office immigration policy after Brexit or strong interpretative reportage about fixed odds betting terminalswill be copied swiftly, dominating other media - the most crucial being the BBC’s running order - and perhaps briefly the national conversation. In a world where it is easy to feel flooded by news and information, the editor’s challenge is not just to act fast but to find ways to change the way people think.