First he turned on the BBC World Service and while I listened to a libido-dampening report from war-torn Georgia, he had a 30-minute shower. He then insisted that I have a shower, too, before we went to bed.

If Dan was willing to exert this level of obsession in the early days of our relationship, what fresh madness was lurking in the weeks ahead? I didn't wait to find out.

It's a cautionary tale. We each have our own set of obsessions and compulsions, routines that we get into and habits that we can't break; Lord knows I have spent years lining up my books by the colour of their spines.

Luckily, I was able to escape early on, but it's not always that simple.

My friend Josh had been in a relationship for three years when his girlfriend began her vendetta against dirt. It started with a spot of light nagging and a tendency to wipe down every surface he touched, and developed into a detailed list of where everything in the house belonged and a cleaning rota that had him doing seven hours of housework a week.

Of course, there's a big difference between [overzealous cleaning and full-blown obsessive compulsive disorder. “People suffering from OCD lose sight of the impact their behaviour has on the other person in the relationship,” says Nadine Field, a psychologist. “Often the person without an obsession feels criticised, not trusted and overwhelmed by the constant reassurance their partner needs.”

And even small obsessions, such as Dan's, can damage a relationship, as Field explains: “Relationships break down over small wounds and they become degraded and diminished each time the obsession arises to cause friction. In the end, both people are frustrated and lose the spontaneity you need to have a healthy relationship.”

Verdict It's a deal-breaker. Don't wait until he's alphabetising your spice rack; get out now.

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