Samantha Cameron spoke from the heart when hailing "amazing" special needs charity Kisharon at a Number 10 reception on Tuesday.
In front of more than 100 Kisharon supporters, Mrs Cameron - whose eldest son Ivan died in 2009 after suffering severe epilepsy and cerebral palsy - said: "David and I understand more than others what a lifeline [organisations like Kisharon] are for a disabled child. To find somewhere to leave your child and know they will be safe, stimulated and happy."
She commended Kisharon for supporting service users from childhood to adulthood, as the transition could feel like a "black hole".
Before leaving to help her pregnant nanny put the children to bed, she wished the "best of luck to everyone at Kisharon for the coming years".
The event marked Kisharon's new property development plans.
Chief executive Dr Beverley Jacobson revealed that "we have purchased additional premises beside our current school in Golders Green with a view to construction of a state-of-the-art special educational needs school for young people aged four to 19".
Added Dr Jacobson - whose 19-year-old daughter Talya suffered brain damage and cerebral palsy after contracting meningitis at birth: "Often, things don't turn out quite as we planned. For some of us, the children we dreamed of are born with significant physical or mental challenges. I stand here as one of a number of women in the room who have had that experience."
Another mother with a story to tell was Emma Castleton, whose 10-year-old son Elias has a genetic condition, Mowat-Wilson syndrome. Elias has blossomed at the Kisharon school and Mrs Castleton said: "It has helped our son achieve things that we would never have thought possible but it needs a more appropriate building. This is amazing news and will take the provision for special needs to a new level."