In these dark days of the pandemic, Prince Charles is shining a kindly light.

It was a nice gesture for Charles to leave a letter on the doorstep of Birkhall, his home on the Balmoral estate in Aberdeenshire, to be collected by Mr Postman - in this case, Neil Martin, who has been delivering mail for 36 years.

Addressed to 'Everyone at Royal Mail', the 71-year-old heir to the throne and his wife, Camilla, Duchess of Cornwall, 72, thanked Post Office staff who have been working right through the pandemic.

There is a photograph of Martin collecting his letter, while Charles and Camilla stood at their front door.

His parents, the Queen and Prince Philip, are far away in Windsor Castle, where it has been announced they will remain for the foreseeable future.

In these days of email, SMS, WhatsApp, Twitter and Instagram, very few bother to send a letter, least of all hand-written using fountain pen and ink. A first class stamp now costs 76p.

The value of Royal Mail workers 'has never been more important' as 'many people have taken the time to write a letter, or a card, to those from whom they are separated', said Charles and Camilla.

'Receiving such a personal message at this difficult and anxious time can mean an enormous amount.

'We feel sure that a very large number of these special greetings will be treasured for years to come. They may even become a valuable resource for social historians in the future.'

This is a very good point because biographers depend on mountains of correspondence to write well-researched books.

'Postmen and postwomen are trusted figures in our local communities,' the royal couple pointed out. 'They are a constant presence in an ever-changing world. For some people, they are a point of daily human contact; a friendly, familiar face.

'Many of you, we know, have gone above and beyond what is normally expected of you. We have heard wonderful stories of postmen and postwomen checking on older and vulnerable residents, raising funds for good causes, even wearing fancy dress costumes to raise a smile....

'Today, as many people - ourselves included - are obliged to stay at home, Royal Mail plays an absolutely vital role in keeping family and friends in touch with one another. For that, we can only say how deeply grateful we are and send you our kindest wishes.'

Meanwhile, people across the UK are being encouraged to shine a light from their homes at 8.30pm on Tuesday, May 12, to show their gratitude to nurses, thousands of whom have come out of retirement to help the NHS.

England's chief nursing officer Ruth May referred to Florence Nightingale, whose image will be projected from Parliament across the Thames on to St Thomas' Hospital, where 'the Lady with the lamp' established the world's first nursing school in 1860. This is also where Prime Minister Boris Johnson received devoted care from nurses.

May said: 'International Day of the Nurse is particularly special this year not just because we mark the 200th anniversary of Florence Nightingale's birth, but because of the extraordinary work all those who have followed in her footsteps are doing in the fight against coronavirus.'