I captured this awesome cloud during a short family holiday in Northumberland last week. I like it a lot.

I guessed it was cumulus congestus but checked with Gavin Pretor-Pinney of The Cloud Appreciation Society:

“Yes, indeed. With a crisp summit like that, it had yet to mature into a Cumulonimbus, at which point the top freezes and looks more blurry. It’s a beauty.”

Feel free to use the larger version for presentations (or whatever).