Clattering Noise

[Tomtom1]

Hi,

Newbie here..

I have a 2005 tdci st that has covered almost 100k miles. Had the car now for a little over 2 years without a single problem. However, yesterday I jumped out of the car to use the cashpoint at tesco and left the wife at the wheel as the car park was packed, a car pulled out of a space next to her so she reversed into it.

As she was reversing into the space I noticed a rattling noise, which after a few attempts at forcing the noise seems to only happen when the car is settling back to idle after being revved slightly. It is quite loud (I was about 40feet away when I first heard it) but its the first time I've ever known it make a noise out of the ordinary, and I'm not particularly mechanically minded so any help will be much appreciated.

Just after a few ideas of likely culprits as I don't want to walk into a garage and sound like a complete novice and get ripped off.

Thanks in advance guys