In the neat, semi-detached house, the kitchen wall is a collage of photos: summer holidays, camping trips, school sports days and football matches. It’s a busy, lively scene in an otherwise quiet house, which is home to Mary and her husband Jack, who are in their late 50s. Their eldest son Richard is 25 and works as an engineer in London; his brother, Max, three years younger, has been missing for 18 months.

Before he left, Max had been offered a promotion at the digital marketing firm where he worked. He’d split up with his girlfriend – and in the past, as a teenager, had had a bout of depression – but otherwise there was nothing to explain his sudden and uncharacteristic disappearance. Soon after he left, his parents discovered money had been withdrawn from his account, and his passport had gone, along with a few items of clothing.

Max is one of the 300,000 young people that go missing every year in the UK, and typical of the many I came across when I was researching my novel ‘A Good Enough Mother’. The triggers for leaving can be varied: for teenagers it’s most commonly family and relationship problems or domestic abuse, and for people in their 20s mental health issues play an increasing part.

For older adults, debt and financial issues can be a factor, with some leaving home to start again in a new place under a new name. While the vast majority of people are thankfully found within 24 hours of being reported missing, some, like Max, are not, and parents like Mary and Jack are catapulted into a nightmarish world of anguish.