Lucy Greenwell

Weeks before that Facebook conversation, her sister Laura had posted a message on a family reunion site asking if anyone remembers the nanny who found the Suffolk baby in 1987.

That post is still out there, languishing in some quiet corner of the internet.

Three years pass and it's only when Jess is leaving hospital, having just given birth to her first baby in 2013, that a sense of being abandoned comes roaring back.

I can really imagine this, that these anxieties could surface at this moment, in those very vulnerable hours after you've given birth.

Jess says she's worrying that she's inherited an instinct to abandon, that she's a bad mother, a bad person.

And then postnatal depression sets in.

And when Jess gets home, midwives drop in on her every day for two straight months.

For anyone who's had a baby in the UK, you know that that's a sign that they're seriously concerned about you.

We know that babies have always been abandoned.

Quite how many, well, that varies across time and place.

In 18th century London, around 1,000 babies a year were left outside churches or hospitals, placed on doorsteps or hidden in parks.

Since the 1970s, a register has been kept of the number of newborns abandoned each year in the UK.

For the 1980s, it shows an average of around 10 babies a year.

But it's far from definitive.

The figures don't include babies who are found dead or those who are later reunited with a parent, so the actual number is likely to be higher.

These days, the numbers are vanishingly small.

Over the last decade, the official figure has never been more than one per year.

But foundlings fascinate us.

Think of Moses in The Bullrushes, Mowgli, Thumbelina, Oliver Twist.

And Oliver Twist's locket, the token that in the novel finally connects him with his family, it captivated readers for a reason, because in the real world, well, there was no locket.