World Hello Day, on November 21st, is celebrated by 180 countries and is intended to illustrate the importance of personal communication in preserving peace. On this day people are encouraged to participate by greeting ten people, preferably strangers.

The positive benefits of briefly interacting with strangers – engaging in eye contact, smiling and exchanging greetings – are incontrovertible. This simple transaction brings with it a pulse of pleasure, a feeling of being noticed and acknowledged, and an affirmation of the belief that humans are fundamentally civilised.

In the country, these pleasant greetings are workaday. In fact, the Countryside Code of 2021 explicitly advises us to “be nice, say hello, share the space”. Life moves at a slower pace in the countryside, so there is more time for pleasantries and for passing the time of day. When you are out walking, it is normal to greet others even if you do not know them, with a cheerful “hello”, “good morning” or “good afternoon”.  On a deserted footpath or windswept hill, where fellow humans are a rarity, it is quite acceptable to prolong the contact by making a friendly remark about the weather, the beautiful view, the toughness of the climb, the muddiness of the paths and so on. These encounters are a heart-warming aspect of country life.

On crowded city streets, however, it is a very different story. Buffeted by fellow pedestrians, deafened by traffic thundering past, acutely aware of a range of hazards ­– from wheelchair users and buggies to young children and oblivious texters – we are likely to beetle along, with our heads down, or with our eyes fixed, refusing to acknowledge our fellow citizens. The Germans have a term for this blank-eyed gaze – wie Luft behandeln – which means “to be looked at as if you are air”, in other words, invisible.

It is undeniable that one of the main reasons for this willed invisibility is anxiety. We are worried that engaging in eye contact will lead to a more prolonged encounter, possibly with someone who is eccentric, threatening or alarming. We fear that our overtures of friendship will be met by routine “What are you looking at?” aggression. This is perfectly obvious on public transport, where there is a near-universal refusal to engage in eye contact or conversation ­ – an unwritten law that is only broken in exceptional circumstances, such as breakdown or cancellation.

Mobile phones have become indispensable props when we do not want to engage. If we fear we are being stared at or are anxious that a stranger might be about to launch into a conversation, we can always rely on our phones. As soon as we start staring at the screen, and especially if we are also sporting headphones, we are impregnable, wrapped in our own cloak of invisibility.

So, if you’re a harassed city-dweller, how are you going to rack up your ten hellos on Monday 21st (and the rest of the year)? The answer is to humanise all your transactions and encounters, and to ensure that you politely acknowledge the myriad people who are offering you a service. Start with a cheerful “Good morning” – this could be addressed to your neighbour as you walk to the bus, the refuse collector who is emptying your bin or sweeping up the autumn leaves, the postman who’s delivering your letters, the bus driver as you tap in, the barista at the coffee shop, the doorman or receptionist at your office building. If you are waiting for a lift and the doors open to reveal that it is already occupied, offer a friendly greeting to the occupants.

Ensure that you greet anyone who is serving you in a retail context, whether it is a convenience store, petrol station, supermarket checkout, or upmarket boutique. When you first encounter them, say “hello” or “hi” and recognise their presence with a friendly smile – there’s really no need to make them feel part of the wallpaper. These are all transactions that you will be having anyway, so you might as well make the effort to turn a mundane encounter into a friendly exchange.

If you’re eating your sandwich on a park bench, take the time to smile and greet the person who sits down next to you. Say “hello” to dog-walkers and people with small children – as long as your greeting is accompanied by a warm smile, they will assume that you are charmed by their dogs/babies and will not react defensively.

All these random encounters are seemingly minor moments in your day, but they will all contribute to an aura of positivity, a feeling of connection and appreciation. You are probably already well aware that when you are the receiving end of a friendly greeting, you also experience a gratifying buzz of acknowledgement, the consciousness that you have been noticed, not overlooked.

It’s a very simple task to put a smile on a stranger’s face and it’s also fundamentally good manners.