And my guilt that he was having to go through it is beyond adequate expression.
I totally blame myself for what happened, even though I had not been there and had no control over the situation he was in. In fact, that is one of the reasons I blame myself.
My son had been at his dad's house, and, of his own volition, decided to try to move a table out in to the garden in preparation for a BBQ. The table had a folding mechanism which trapped and crushed his hand, severing the tip of his finger, ripping off his nail and fracturing his bones.
It was a beautiful Sunday afternoon. I was at my desk playing catch-up on some work when I got the call. Somehow, I just knew it was something awful as soon as I saw my ex's number flash up. He would only call me at Sunday lunchtime if there was a problem.
At the hospital we were asked horrid questions which just made me feel worse about our fragmented life: Was our son known to social services? Who does he live with? Who else lives in the house?
The following morning he had surgery. Maybe because of the information on the forms – I do not know what it actually said; perhaps our estranged status was flagged up in some kind of code – no one seemed to address his father. "Mum, this is what will happen," they told me. "Mum, we are going to take him down to theatre now." "Are you all right, Mum?"
Three different people asked me if it was my signature on the consent forms. If that was the correct name on his ID tags.
When he came round, only I was allowed in recovery.
Back on the ward, 'Mum' was told about his meds and ongoing care.
'Mum' was told at discharge to phone at any time if there was any concern about his wound.
'Mum' meanwhile was on autopilot, consumed with a wretched sense of how her life choices had led to this point.
Every parent feels an excruciating sense of blame, responsibility and fear when their child is hurt or unwell. But having experienced it as both part of a couple and now as a single parent, for me, the latter is so, so much harder to endure.
Not only the sense that you have no one there in a touchy feely, supportive, huggy kind of way to share it with, to make your own passage through it easier, but the complete and utter feelings of guilt that your child has been hurt and is hurting and you were not there when it happened.
Guilt that I hadn't been there to soothe and reassure him on the way to hospital.
Guilt that one of his perfect little hands – that even at nine still had their clutchable baby-like chubbiness – would never look the same.
Guilt that his father felt excluded and ignored by his son's care-givers.
But mainly, overwhelming guilt that I am bringing my child up in an environment where things can happen that I am unable to predict or prevent because I am simply not a part of, or involved in, some of his day-to-day life.
Do you feel immense guilt as a single mum/dad if something upsetting happens to your child when he or she is with their other parent?