Positioning of HTML elements with css

Positioning of HTML elements with css

HTML Code
<header>
<h1>Event Heading</h1>
<div class="meta">09 JUL 2014</div>
<div class="textblock">Lorem ipsum dolor sit amet, consectetuer
adipiscing elit. Donec odio. Quisque volutpat mattis eros. Nullam
malesuada erat ut turpis. Suspendisse urna nibh, viverra non, semper
suscipit, posuere a, pede.</div>
</header>
Issue
I have this HTML structure which I can not edit/rearrange. I would like to
position the h1, div.meta and div.textblock is as in the picture below.
I can't work it out with floats the way I want to because of the sequence
of the HTML.
Illustration