Those of us who know CFA have seen photos of the barrels of his old .465, and George and J. J. have looked it over carefully as well. I don't think any of us believe it to have been a pressure burst (overload, obstruction, etc.). The hole is way too neat for that, and too free of distortion. Either a flawed or damaged barrel.

Some have floated the idea that the pre-WWI nitro proof barrels are automatically suspect. This is based on the premise that most of the rifles that have blown are pre-WWI, thus the steel must have been bad then. For example, of the five rifles that George's clients have had blow, four were pre-WWI (and three were Hollands). I don't find that significant at all. Learn how to date them and go someplace where there are a large number British double rifles. See how many you find that are post-WWI for sure. Of course most that have blown turn out to be pre-WWI, that's when most of them were built.

After monolithic bullets were introduced, many fine doubles were wrecked with them, solid and expanding types both, before the word got around. And of course, the proverbial deaf, dumb, and blind 10 percent are still with us, and probably always will be. A rifle with barrels that have been struck off and re-blacked (as CFA's first Holland was) is nice to look at, but if they were struck off and re-blacked to hide evidence of severe overstressed rifling.....This damage is worst down-tube, where the barrel walls are thinnest. Mick's comment about the barrels bursting in the same place being due to excessive pressure down-tube is not without merit, but I can also see how this might happen with a normal load in barrels that were damaged in this same way. Of the five rifles mentioned above, IIRC, the four pre-WWI rifles blew down-tube. The one post-WWI rifle was a .500 Nitro that blew out the chamber wall while shooting new Westley Richards factory ammo.
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