Highlighting current page

I have the following in my website:

<div id="menu">
   <ul>
	 <?php wp_list_pages('title_li=&depth=1'); ?>
   </ul>
</div>

Which lists all top level pages in a horizontal menu bar. Works perfect.

My CSS also has a mouse-over event to highlight each page name before the user clicks.

But I’d like to enhance my page by having the current page already highlighted with a particular class.

I’m trying to get my head around how this could be done.

Does anyone have any good pointers please, bearing in mind it would be nice to have some kind of code that could ‘grow’ and ‘shrink’ depending on the pages in my site.

TIA