Strange behavior with URL fragments and onclick in iOS Safari

Question

I have run into a strange problem in mobile Safari on my (iOS 4) iPod touch. The minimum body HTML to demonstrate this problem is:

<p>
    <a href="" onclick="event.preventDefault()">Click</a>
</p>
<p id="anchor">
    Anchor
</p>

When the page is loaded with no # fragment in the URL, clicking the link executes the onclick javascript, which suppresses the action of the link, and (as expected) nothing happens.

However, if the page is loaded with a valid URL fragment, #anchor in the above example, then clicking on the link causes the page to jump to the paragraph with id 'anchor' (like when the page was initially loaded).

I cannot find a way round this; any suggestions would be greatly appreciated.