During the Second World War, in 1943, four schoolboys hopped over a fence and went looking for birds’ eggs in a private wood just to the west of Birmingham. One of them clambered up a strange squat tree, in the hope of finding a nest at the top. But he got rather more than he bargained for, because when he peered inside the hollow trunk he discovered a human skeleton.

The body in Hagley Wood went on to be one of the strangest and most baffling cases of the last century. It was found to be a woman who had been murdered around two years previously. However, dental records could give no clue to her identity and the police investigation encountered a wall of silence when they tried to talk to local people.

A couple of things made the murder a particularly odd one. The first was that the woman’s right hand had been deliberately severed. And then there was the graffiti. Initially, it appeared in a street in Birmingham in 1944 and later on an obelisk at the top of a hill near Hagley Wood. The graffiti re-appeared several times over the years until the 1970s, always asking the same question: Who put Bella in the Wych Elm?

The mystery is still unsolved although theories have not been in short supply. Some say the severed hand suggests a black magic connection, one even claiming that the notorious English occultist Aleister Crowley was behind it. Others believe the woman was executed as a spy who had parachuted into the country to join her German lover.

The Hagley Wood Murder was one of the many stories about trees which intrigued me, as I researched the background to Annie’s Oak. The idea that some trees are haunted is a fairly common one. The countryside was once dotted with hanging trees, used as gallows from which the rotting bodies of criminals hung. Giant ancient trees have long been celebrated as hiding places for fugitives from Robin Hood to King Charles II. And there is also something creepy about the thought that trees are the only living things that have been here longer than we have – and that they will almost certainly outlive us too. I discovered there was an ancient yew tree in a Welsh churchyard that some believe to be around 5000 years old – about the same age as Stonehenge!

These were the kind of thoughts that were swirling around in my head as I settled down to write Annie’s Oak. The story is not directly taken from any of them but, as is the way with so many ideas, it owes a bit of a debt to them all.

It is set in Sheffield – a city known both for its trees and for its fierce resistance to the felling of them. I’ve never lived there but I’ve always really liked the city. It seems to me it’s just the right size for fiction. It’s small enough that you can stand in the city centre and see the green hills beyond. And yet it’s big enough to contain all the diversity, the mystery and the history that make it seem like a place where anything can happen.

It has been the setting for a number of memorable films – Four Lions, The Full Montyand The History Boys all spring to mind – but it feels strangely under-represented in literature generally. (Or perhaps I’m missing out on something – if so, do let me know.) However, the city has certainly contributed more than its fair share of fantastic songwriters and musicians. There is a Pizza Express not far from the station with a mural depicting some of its finest – I seem to remember The Human League, Pulp, Def Leppard, maybe Joe Cocker too?

And as I wrote the story, I played and replayed The Last Shadow Puppets’ The Dream Synopsis, with Alex Turner’s gorgeous line about the wicked gale howling through Sheffield city centre - which is, of course, exactly what happens in the story…