My parents chose to die together and I was left to grieve alone

Bas found a parking space.

"My dad said goodbye to my car - he liked my car, and he said, 'Good job', and 'thank you'.

"And then we walked inside," Bas says. "Imagine doing that - being in their shoes, taking that trip and that walk. It's so unreal."

For the next two hours, the couple's family and friends came and went. They reminisced, and listened to music. At one point, it crossed Bas' mind to call a halt to the proceedings.

"I had a feeling - 'OK, let's leave… Let's step into the car and drive away,'" he says. "But I didn't want to bring anything up that would make them feel uncertain - I had supported the whole [euthanasia] process.