The stay ends at the dropouts would also follow the curve of the stays if this were built as such. A close look at the domed end indicates that they once pointed directly at the seatlug cluster, not forward of it.
I'm not convinced for one solitary instant second that it was built like this, no matter what some want to believe. However, I don't believe this is the result of a crash. With Hetchins being a prominent English brand at the time, this looks like an
intentional modification. Someone wanted the look of a Hetchins and couldn't afford it. Some careful cold-setting (and likely a lower BB later), this was the result.
I wouldn't be surprised if some equally careful adjustment could straighten this mess back out again. I'll bet anything the top tube slopes slightly as the length lost by curving the seatstays would have raised the rear chainstays and subsequently the rear drops. It would also account for the longer Weinmann brake caliper being out of place. With the stays straightened, the caliper would be reaching further rearwards to access the curvature of the rim - meaning the brake pads would have to come down in their slots to meet the braking surface, and thus explaining why it was spec'ed in the first place.
Also, just a reminder to those who haven't run a Google search, every other Carlton Cobra out there looks like the ones below, with differences primarily in livery per year. Most importantly, not a single one of them demonstrate curved stays.
I said it before, and I'll say it again: Someone wanted to stand out like a Hetchins, and knew someone crafty enough with cold-setting to do it. It's doable.
-Kurt
EDIT: Oh, great. Suckered into a zombie thread again. 