In August of last year, Google introduced in-depth articles in the US search results. Since then, Google has upgraded the design and functionality of those articles a couple times.
Now, Google announced on Google+ that the in-depth articles are now going to be showing up in the UK search results.
Google said, "over the next few days we'll be rolling out a new feature to help you find relevant in-depth articles in the main Google Search results."
Here is a picture of what they may look like:
Forum discussion at Google+.