One must always wear headphones when watching video, take care not to be “a table-hogger”, and one must not – in any circumstance – look askance at a crying baby.

Those are the cardinal rules of working from a cafe, according to the etiquette bible Debrett’s.

The 253-year-old British institution, which once advised women to avoid using “vulgarisms, flippancy, coarseness, triviality or provocation”, has turned its attention to the modern trend of working from public spaces.

In a new guide titled Cafe Rules for Digital Nomads, Liz Wyse, Debrett’s etiquette adviser, explains when it is appropriate to make video calls in a cafe (never) and how often to order food or coffee (at regular intervals).

“Cafes need turnover to make a profit, so you must not turn into a table-hogger, who nurses a single cup of coffee while other customers come and go,” intones the official advice.

Workers should remember that cafes are a place for people to socialise and chat, so do not glare if you find the noise disturbing: “You must never look askance at your near neighbours because their animated conversation or crying baby is playing havoc with your concentration. That is your problem, not theirs.”

Founded in 1769, Debrett’s started as a guide to the British aristocracy but branched out in the mid-1900s to become the unofficial rulebook on “British style, correct form, modern manners”.

The rise of hybrid working during the pandemic has had a mixed reaction among cafe owners. Many have welcomed the extra custom but others have banned laptops after 5pm and complained about workers hogging tables without buying many drinks.

Last month, Costa Coffee launched a limited trial of soundproof booths with charging points in a number of its stores for customers willing to pay £13 an hour.

The trial, in partnership with My Work Booth, is in two stores in Manchester and two in London but will be extended in the coming weeks.

For those who have no option but to work amid the clatter and din of a busy cafe, Debrett’s has the final word.

“You should avoid video calls or conferences when you are working in a cafe, as you will look unprofessional,” said Wyse. “You don’t want colleagues or clients to get the impression that you are casual about your work commitments.

“If circumstances arise where you have no choice and have to join a video call, explain where you are and apologise for your backdrop. When you are not speaking always remember to mute the sound, otherwise you will deafen your colleagues with clattering coffee cups and chattering customers.”