Ordinarily, the Princess of Wales is a glamorous mainstay of the summer season, stepping out at Chelsea Flower Show, Buckingham Palace garden parties, Trooping the Colour, Royal Ascot and Wimbledon.

This year, however, she will be convalescing at home, out of the public spotlight, as she continues her chemotherapy treatment for the cancer that was discovered after abdominal surgery earlier this year.

Prince William cut a slightly lonely figure as he hosted the Sovereign’s Garden Party without the Princess by his side, although he had called in his cousins, Princess Beatrice, Princess Eugenie, Zara Tindall (plus husband Mike with whom he is close) and Peter Phillips to boost the royal roster.

He has been the epitome of ‘keep calm and carry on’ as he juggles public duties and private support to his wife and young family.

As William joked about the torrential downpours being ‘good weather for swimming’, he also shared optimistic updates on the Princess, saying she is ‘doing well’.But in truth this has been an extremely tough time for both Catherine and William, as they remain committed to maintaining a sense of routine and normalcy for their three children, George, 10, Charlotte, nine, and Louis, six.

The Princess has continued to do the school run, and attend their sports matches and ballet classes, when her treatment and fatigue allows. And in an encouraging sign, she has been working behind the scenes on her early years project and is ‘excited’ by its progress.

Earlier this month her Royal Foundation Business Taskforce for Early Childhood launched a new report which said prioritising young children and supporting their caregivers could lead to ‘£45.5 billion in value added for the national economy each year’.

The report is intended as a ‘blueprint’ for businesses of all sizes and functions, to lay the foundations for making small changes to improve opportunities for parents, carers and children in society.

Its five recommendations are to be translated into practical action that suits an individual business. Examples range from businesses not scheduling calls before 9am, enabling working parents to complete the nursery or school run undisturbed, to subsidised or on-site childcare, and adding family-friendly food labelling to ensure healthy choices.

The taskforce, established last March, is made up of Aviva, The Co-operative Group, Deloitte, Iceland Foods, IKEA, The LEGO Group, NatWest Group and Unilever UK – all of whom have committed to early years programmes within their own companies.

This is a real passion project for the Princess – she has said it will be her life’s work – and Christian Guy, executive director of The Royal Foundation Centre for Early Childhood, said: ‘What is so important for her is action. She feels passionately about the transformational impact of getting this right together, both for the current generation and for many more to come. To have eight significant businesses in Britain making the case to their fellow business leaders is exciting for her. And it’s a priority going forward for our centre and her work.’

The report, produced by Deloitte on behalf of the Taskforce, found the national economy could benefit some £12.2 billion from ‘equipping people with improved social and emotional skills in early childhood’, £16.1 billion from ‘reducing the need to spend public funds on remedial steps for adverse childhood experiences’ and £17.2 billion from ‘supporting parents and caregivers of under-fives’.

Behind the scenes, William’s focus has been on steadfastly supporting his wife – and he has been encouraged that her work has brought her such fulfilment at a very difficult time.

He has also had to deal with his father’s cancer diagnosis, the ongoing feud and fallout with his brother Harry and the huge responsibility as heir to the throne. ‘He’s definitely had to dig deep’ says a friend. ‘Whether you’re a prince or pauper, no one would expect anything like this with his father and his wife both being treated for cancer.’

King Charles returned to public duties last month, although he is also still undergoing treatment for his unspecified cancer. This week the Royal Family will be out in full force to commemorate the 80th anniversary of the D-Day landings – the Prince of Wales, Princess Royal, King and Queen will be in Normandy, with the Duke and Duchess of Edinburgh at the National Memorial Arboretum in Staffordshire.

But the Princess of Wales will not return to public engagements, as Kensington Palace has always said, until she has the ‘green light from her doctors’.