A photograph of a couple grinning outside two red phone boxes. A nice but seemingly unremarkable picture. The caption beneath it on Facebook gives it further context: a passing stranger was commandeered by the couple to capture the moment just after the man had proposed and was accepted. The picture goes from ‘nice but unremarkable’ to ‘lovely’.

The grinning woman is my Mum. The grinning man is Andy, her fiancé.

What takes it from unremarkable to the lovely thing it really is, is the extra context that is left out of the photo’s caption. Mum’s secret history of the setting.

The phone booths are in Billericay, where she grew up as a fostered child from the age of two. Her sister, six years older than her, remained with their father and their mother, who was confined to a wheelchair after a stroke rendered her immobile down one side. I won’t relay details of my aunt’s or my grandmother’s life, but Mum had a severely lucky escape.

Nevertheless her childhood was not a happy one. Living in the austere environment created by her very Victorian foster ‘mother’, Mum still visited the family home every fortnight, in an awful decision made in its naive nascency by the social services. Caught between the two, Mum missed out on love, security, and a sense of belonging.

Mum remembers the visits. She remembers her sister making her hide behind the giant wheels of her father’s army truck as he stumbled around looking for them; she remembers her pushing a chair under the door handle of the bedroom at night. She remembers wanting her mother, but being afraid of the limp woman in the chair, whose only barely audible utterance was “she’s mine”.

Mum texted me after the proposal: “Andy didn’t know that the phone boxes where he proposed held memories of such an unhappy period in my teens. Now completely obliterated by his love. I am a very lucky woman.”

I wanted to say she is not lucky, but that only now in her fifties is she getting merely an ounce of the happiness she has deserved all this time.

In her teens Mum went to the red phone boxes everyday to phone her social worker to try and get her out of the foster home where she was desperately unhappy. Daily she would plead her case for her own future. Those glassy booths of dubious privacy I suppose became symbols of her feelings of anguish, hopelessness, and repeated rejection. They are now symbols of love – and the sense of home and peace and belonging that comes with it.

Something in the simplicity of the picture jarred me more than the girlish excitement of the conversations I’ve had with mum about her wedding, her dress, more even than the repeated exclamations of “I’m just so…happy, Sadie!”

I’ve been writing a book about my Dad. A very difficult man whom Mum could write her own very different book on. (Who’s dead by the way, if you’ve missed my more maudlin columns.) The book is about loss and grieving and all that sort of waily stuff. Writing it has made me recede from a lot of things.

The phone box picture made me see that I have been overlooking the people that are still here and to be cherished too. In trying to do the right thing for my Dad, I think I stopped doing the right thing for my Mum. I’ve been down a hole. Slow to get on board with her new relationship. I’ve felt cautious. But the picture, with the split second of loaded meaning it captured, has brought me back.

I finish this column here because I’ve gone all blurry. Happy tears, for the living. For my mum, and the man who brings out the girl in her, all fresh and new.