One moment I was with a friend, admiring the dappled sunlight in London’s Hyde Park, the next my head was spinning, my knees had given way and I collapsed to the ground.
Lying on the floor in a public place, unable to get up unaided, was not only embarrassing but also incredibly nerve-racking. Nothing like that had ever happened to me before.
I called a taxi to take me home, where I climbed into bed, hoping a good night’s sleep would make me feel normal again.
But it didn’t. Over the next few months, I was paralysed with exhaustion. To the extent that from March 2014, I would go on to spend three years in bed.