The (Digital) Discovery
The initial discovery, it must be said, was entirely accidental. I was working on some graphics for a smartphone app about Stonehenge, and we needed some imagery for the Bluestonehenge section. We were hoping to use the paint & paper reconstruction of a well-known artist, but he was on holiday at the time and we needed something right away, so I resurrected an old Sketchup model I’d made back in 2009, and dropped it onto an image taken by Adam Stanford during the excavation – like every other reconstruction to date, it was round. I then took a couple of screengrabs and emailed them to Adam so he could see them while we discussed the matter during a video chat. He made all the right encouraging noises, but pointed out that I’d missed the hole on the far right. This prompted me to return to the model and increase its circumference to take in the ‘extra’ hole. Now it looked too large, and it didn’t really fit all that well.

To get to the bottom of it I went back to the beginning, opened Adam’s image in Photoshop and began experimenting with the elliptical marquee tool to get an idea of the possible layout of the unexcavated post holes. It quickly became apparent that an oval layout matched the excavated holes far better than a circle did. Having kept back a single pillar from the original model, I then rebuilt Bluestonehenge as an oval. It worked, I took a couple of screenshots, sent them to Adam and then posted them on my blog with a short write-up, thinking it was an observation that other people might find interesting. I also mailed a couple of people who I knew were involved with the dig to get their opinion.

The 'Bluestonehenge' excavation. With oval overlay. With digital stones in place.

The Comparisons – Bluestonehenge, the Bluestone Oval at Stonehenge, Woodhenge and. . . Bedd Arthur?
One of the people who responded first was Mike Pitts, who discussed the new model on his blog (Digging Deeper). One of the things he wrote that particularly caught my attention was that a “corollary of being oval, rather than circular, is that you have an orientation” (Pitts, 2011). He also mentioned two other ovals in the area – the one inside Stonehenge, and the one at Woodhenge. I had models of both knocking around on my hard-drive, so I brought them up and pasted my oval into the models. All the models were geocoded, so I knew that the orientations would be as they were in the real world. I tried Stonehenge first, and, in an eyebrow raising moment, saw that my oval fitted the Bluestone Oval exactly in size, shape and orientation.

Overlaid sites in Sketchup. See PDF for key. Overlaid sites in Sketchup. See PDF for key. Aerial shot of the Woodhenge with internal ovals highlighted. The above chart, with a key to the coloured dots and how they relate to the sites in the text is available as a PDF - click here to download.

The size would change in a later revision, but the shape and orientation – arguably more important than size – was a particularly good match. I then tried the same experiment with Woodhenge, and got a very similar result – my oval was slightly larger than the central oval at Woodhenge, but the alignment and shape was an excellent match.
Again, the size would change, but again, the shape and orientation wouldn’t. Following the suggestion of a follower on the Digital Digging Facebook page, I had a look at another bluestone oval, that of Bedd Arthur. I couldn’t find any site plans (I understand not a great deal of work has been done at the site) so had to build a model using perpendicular satellite images, and photographs taken from the ground. This isn’t an ideal method – it’s always good to have a site-plan to hand – but it can result in a perfectly good approximation for a working model. The match this time wasn’t so good – the alignment was fine, but the shape was very different. Bedd Arthur is more of an elongated tear-drop than an oval, and also displays a much lesser degree of symmetry than any of the other sites mentioned here. It is, none-the-less, of interest that its orientation, size, and the material used in its construction are  the same as the Bluestone Oval at Stonehenge and is worthy of further investigation.