Spoiler warning! Watch where you tread, there are some spoilers ahead – turn back now if you’re not familiar with the books…

Firstly, who were the Dursleys?

The Dursleys were a Muggle family who took an extraordinary amount of pride in their ordinariness – Vernon Dursley even had a moustache comb. If that wasn’t monumentally mundane enough, they lived in an extremely ordinary house on a totally normal street – number four, Privet Drive.

Petunia was Harry’s aunt and the only sister of his mother, Lily – their similarities ended at their floral names. Where Lily was kind-spirited and welcoming, Petunia was mean and narrow-minded.

Her husband, Vernon, was a director of the drill-making firm, Grunnings. A respectable job to match his respectable car and respectable family. Having a witch for a sister-in-law? Not respectable.

Together, they had their son and apple-of-their-eye – Diddykins (otherwise known as Dudley). Some would call Dudley boisterous while most others would call him a spoilt bully.

We also had the unfortunate honour of meeting Vernon’s sister, Marge, but the less said about the incident which was… blown completely out of proportion, the better.

By the time Harry arrived on their doorstep, Vernon and Petunia Dursley were not close with Lily and James Potter. Actually, after a disastrous dinner at a restaurant, Petunia not having Lily as one of her bridesmaids, and Vernon referring to James as an ‘amateur magician’, they weren’t on speaking terms.

Ok, but why were they so horrible to Harry?

With an introduction like that, it’ll come as no surprise to learn that the Dursleys were very prejudiced people. Anything that they didn’t understand, they feared – including magic. Something that unusual couldn’t be good and that included Harry.

There is one other reason to consider here – jealousy. Did you know that Petunia had wanted to be a witch too? She had even written to Dumbledore as a child to ask if she could go to Hogwarts. Although he let her down gently, Petunia’s resentment towards her sister and magic continued to grow. Eventually, magic was no longer the thing she most wanted, it was the thing she most despised.

Harry was a living, breathing reminder of Petunia’s pain and a threat to the carefully curated image of her family. There would be no greater disaster than if the neighbours found out who Harry truly was – how could they bear the scandal!

Surely, they had other family who could take Harry in?

Well, with that history, leaving your only son to live with the sister who threw his birth announcement in the bin is… not ideal. But, when Voldemort murdered Lily and James Potter, there wasn’t another choice. Lily didn’t have any other living family.

On James’ part, his parents Fleamont (the creator of Sleekeazy’s Hair Potion) and Euphemia, had passed away. Born after Fleamont had retired, James was their only son – a wonderful surprise after they had given up any hope of having a child. Although they lived long enough to see him get married, Dragon Pox claimed them both before they met their grandson.

Or literally anyone else?

Outside of their blood relations, the people that were closest to the Potters were not in any position to take Harry in. The Marauders had broken apart completely – Peter was thought to be dead, Sirius was locked up for Peter’s murder and Lupin had retreated to the outskirts of society.

Plus, while we’re sure that lots of wizarding families would have jumped at the opportunity to take in and raise the Boy-Who-Lived, Dumbledore thought that there might be a deeper magic at play – making this impossible.

Couldn’t he live somewhere else once he knew he was a wizard?

It’s true that Harry felt more at home at Hogwarts than he ever had at the Dursleys. He was no longer the lonely little boy in the cupboard-under-the-stairs – and not just because everybody here knew who he was. He had finally found his people – from his best friends to his godfather and everybody else who was there for him.

Except, none of them were related to him by blood. More specifically, none of these people shared his mother’s blood. This is the crucial point. Even if James’ family had been alive, Harry couldn’t have stayed with them – and it all goes back to the prophecy.

When Professor Trelawney spoke of the one person who could vanquish the Dark Lord, Voldemort believed that meant Harry Potter. Determined to eliminate any threat to his power, he decided that the Potter family must be killed.

Surprisingly, one of his most loyal Death Eaters, Severus Snape, asked him to spare the life of Lily Potter. So, when Voldemort arrived on that Hallowe’en night in Godric’s Hollow, he gave Lily a choice. If she stepped aside and allowed him to kill Harry, he would let her live. She refused. He murdered her to get to her son.

Except, Voldemort did not know that Lily’s sacrifice had unlocked an ancient magic. When she gave up her life to protect Harry, that protection lingered – flowing through his veins and making it impossible for Voldemort to touch him.

Suspecting this, Dumbledore took Harry to live with the only other person to share Lily’s blood, Petunia. Despite being incredibly reluctant, bitter and furious (amongst other things), Petunia brought Harry into her home, sealing the Charm Dumbledore had placed – the bond of blood being the strongest shield he could give him.

As Dumbledore explained in a letter to Petunia, while Harry could refer to the place where his mother’s blood still dwells as home, Voldemort could not harm him. Even if he only returned once a year. Even if it was miserable for him there. Even if the Dursleys resented him. As long as number four, Privet Drive was his home, the magic would continue to work. Harry would be protected, and Lily’s love and sacrifice would be honoured.