Katy Perry may have spent the last month as one half of the most loved-up couple in all of celebland, but she was brought firmly down to earth this week by a rather personal question.

According to the Daily Star, the singer was out enjoying an innocent spot of shopping (without Russell Brand for once) when a male fan took it upon himself to ensure that the couple were being careful in the bedroom.

Apparently, while she was happily coping with all the press attention and crowds of staring shoppers, the 'fan' shouted: "Katy, have you and Russell gone and had STD tests together yet or what?"

Whatever could he mean, we hear you cry.

Well, he clarified rather nicely: "It's just the smart thing to do. There's a lot of things going around and your fella has been putting it around all over the place."

Now, that might not seem like a very nice thing to say, but bearing in mind Russell's track record with the ladies, he's kind of got a point.

Anyway, it was enough to send a "mortified" Katy scurrying angrily back to her car.

Katy may be in the process of taming Mr Brand, but he does have a reputation for being a celebrity swordsman...