The therapy attempts to alter behaviour, but it appears to alter much more than that. Dr Sanjaya Saxena, the director of a programme for obsessive-compulsive disorders at the University of California at San Diego, said that exposure response prevention therapy “certainly is changing the brain at the molecular level — that is, at the level of particular proteins that are expressed and created and on the level of neurotransmitter function.” In that sense, he said, “behavioural therapy is biological therapy.”

I am no brain scientist. I understand almost nothing about proteins and neurotransmitters. But my own work with this treatment has progressively allowed me to take back much of the life my disorder stole from me. Now when I say check, please, I’m simply asking for my bill.