I’m fiercely protective of my girls – like a lioness

blossom. I know it sounds like a fairy tale but that’s the way we are.

‘And the Sunday after the wedding, I said to Eugenie and Jack: “Do you want to stay somewhere special?” no. They wanted to stay at Royal Lodge. So the night before their honeymoon, the whole family were eating pizza together in the kitchen.’

On her closeness to the Queen — who reportedly remarked that whatever Fergie has done, she has always been a good mother — she is judicious: ‘Her Majesty is the finest icon I’ve ever been lucky enough to share a room with. She’s the most exceptional Head of State, lady and mentor. I am very fortunate to know her.’

SHE is equally full of praise for Prince Philip, whom she describes as ‘an incredible man’. ‘I have huge respect for him and always admired him. It was a lovely photograph of us all together. It was very good to be with him again. My father and he used to play polo together. It brought back memories of that.’

It is for being a good mum that Fergie is justifiably celebrated. She says she and her daughters are a ‘tripod’ — an interdependent and solid threesome.

Over the years, the princesses have endured crushing criticism: Beatrice, particularly, has been vilified for her shape, size and dress sense.

The Duchess will not be drawn to comment, other than to say: ‘I am fiercely protective of my girls. I’m like a lioness.’

It’s indisputable, too, that the Yorks provide a paradigm on how to parent well after a divorce.

‘Of course we’re human, both Andrew and I, but when we walked through the door we never brought our adult problems to the children. This is always our rule.

‘And you’re always honest with your children. When they say, “Mummy, what’s happening?” you say, “It’s interesting you should ask the question,” and you explain in a way they can understand.

‘When my parents divorced, I didn’t have a parent who was telling me the truth. I found out in 1974 through a newspaper what was happening.

‘And I felt … I believed, that I had done something wrong. I think it’s really important that children don’t feel that. The fact that we divorced had absolutely nothing to do with the girls.

‘But I remember thinking I was responsible for my parents splitting up — because I’d cut my hair.’ She laughs ruefully at the memory. ‘And because I wasn’t good enough. And that was when I began to comfort eat, and why I’ve had a weight problem all my life.

‘It’s why I have total empathy with what it is like to be destroyed by self-hatred, because when you comfort eat you put on weight, and then beat yourself up for comfort eating. It is such a vicious circle.

‘I comfort-ate all my life from the age of 13. I started when I was at boarding school, when I heard my parents were getting divorced. I got up to 14-and-a-half stone.’

Today, she looks enviably slender in a flirty flared skirt teamed with Smythe jacket in racing green. The ‘soul-destroying’ Duchess of Pork jibes that dogged her when she was at her heaviest are now palpably inapplicable.

Her jewellery is trademark Fergie: a gold bracelet bearing her girls’ names picked out in diamondencrusted capitals; a super-sized Remembrance Day poppy blooming from her lapel.

Once she has kicked off the Jimmy Choo heels she wears (at our request) for the photos, she slips, with relief, into flat velvet pumps embroidered with unicorns. They seem to sum up her spirit: fanciful, child-like, princessy. If you asked Fergie her favourite colour, she might well say ‘glitter’.

She seems an amalgam of contradictions: childlike but pragmatic; jolly yet reflective; robust and hearty at times, then fragile.

‘It has taken me 59 years, but I’m happy to own this sense of joy I feel now,’ she says. ‘My mantra is the Hs: honour, humility, hope and humour. If I have ever let anyone down, and I am sure I have done so at times, I have always tried to amend and do my best. I believe in forgiveness for myself and for others. It’s an important quality.’

She admits to having felt ‘sadness’ in her past but is careful to distinguish this from depression. When she feels low, she says, she has a strategy for coping. ‘I take a bit of quiet time; maybe watch a black and white movie and make myself cry even more. (Cary Grant is one of my heroes.) But I love to laugh, too. I find a sense of humour always helps.

‘As my grandmother would say, “This, too, shall pass.” She brought me up to clean my side of the street — by which she meant to forgive and never let the sun go down on an argument.’

I ask if she has learnt to cope with the loneliness of successive Christmases spent without her daughters. This year will be the 22nd, since her divorce, that her girls have gone to Sandringham to join the Royal Family, while she, uninvited, will stay home alone.

AND once again, Sarah is generous- spirited. ‘I know that Her Majesty adores my children, so I am happy to share them — both in August and at Christmas.’

I ask if it breaks her heart to be a distant observer of this close, familial happiness, but she replies with customary bravado: ‘no! I am happy making other people happy. I really am like this. I love to share. It’s the joy of giving.’

She gives a lot of time and energy to her charity work: she is an Ambassador for the British Heart Foundation and is talking to me today to promote the launch of Street Child, newly merged with the charity she set up in 1992, Children In Crisis. She is passionate about the role education plays in lifting people out of destitution. ‘At Street Child, we all believe that education is a fundamental right and that it is a scandal and a tragedy that there are 121 million school-aged children around the world who are not able to go to school,’ she says.

Tom Dannant, who established Street Child in 2008, says: ‘It’s a measure of the Duchess’s lack of ego that she was prepared to merge her charity with our faster-growing one. She thought it would pack a bigger punch and she could do more to help children that way.’

He reports, too, on her passion, stamina and willingness to endure privations. ‘Earlier this year, we drove through rough, winding roads in nepal for ten hours, then stayed in a cockroach-infested hotel. She did it to reach the children in greatest need.’

I ask Sarah about this trip and she throws up her hands and laughs. ‘My father would have called it character-building,’ she says. ‘They shovelled me in a car and we wanted to find these children who literally had nothing.

‘The monsoon rains were coming, they had no food and the water they drank was polluted and infested with cobras. And the hotel was one of those where you sleep on your suitcase because it’s more comfortable than the bed.’

The charity will be building a school in this remote and impoverished outpost: Sarah has already forged links with some of the children it will educate. ‘My grandmother always used to say Proud mum: Sarah with Beatrice, left, and Eugenie to me: “If you feel down about life, then go out and give to others”,’ she recalls.

And there is no doubt in my mind that Sarah’s compassion, her empathy — actually her love — for children is genuine. Visiting Julia’s House, a children’s hospice in Wiltshire with her, she blows in like a gust of fresh air, dispensing sweets and trinkets, joining a craft session, decorating a cake (with unicorns) and reading from one of her Budgie the Helicopter books.

Those who would decry her choice of reading material as opportunistic might do well to recognise that the stipend she received from the Royal Family after her divorce was reputedly just £15,000 a year. She needs to earn money, and does so through a series of creative enterprises.

She shows me her range of teas — ingeniously concocted to smell and taste like the deserts she adores ( there’s jam roly- poly, chocolate tart, strawberries and cream) — which have helped her resist puddings and keep her weight down. (Some of the profits from sales will go to Street Child.)

She gently cajoles her young audience, remembering their names, chatting on their level.

LATER she confides to a group of parents: ‘I prefer to be with children because I can be with my imagination. What I take away from any visit like this is the kindness, the love, the children and the total joy. I love the atmosphere and goodness here.’

I ask if she’s looking forward to being a grandmother. She laughs.

‘How many children’s books have I written? Twenty-two! Frances, I tell you, they’ll be older than me at age three! I’ll have more fun making the Barbie kit houses than the grandchildren will.’

This is, perhaps, the essence of Fergie: to be child-like is to be released from the obligation to conform to adult expectations and conventions. ‘When I got married people said: “You mustn’t make faces when you go out. You mustn’t do this or that.” But I just want to be myself. I’m 59 but I feel about eight years old.’

I leave the Duchess freighted with gifts from her. There’s a silk scarf (woven by trafficked women), a selection of her tea bags, china wedding mementoes, shortbread — a veritable goodie bag.

As she hugs me, she says, ‘I like to have harmony. People say it’s people pleasing, but it’s the way I like to be. It makes me feel good.’ To support the work of Street Child, visit www.street-child.co.uk