Lol what have you done put the tube in the freezer then warmed up half with a warm tea towel?

@kev, you would have thought so, wouldn't you?! But no. Straight out of sleeve from storage.

I've had it happen to a few (no Thorns though), including some NOS Philips 75W 840s, and a recent Narva 15W Red. Tested fine but after a year of being unused they were (...)ed. Only ever seems to happen to unused lamps, which have been run for only a few hours as a test and then not used again for some time. Maybe they ought to be aged for 100 hours?

I'm not too sure what happens to these tubes and why, I've had quite a few 5 and 6' where the ends fall off 8' seem ok don't seem to suffer and weirdly I've had a few 3' fail.

I can replicate this with the 6 foots at work, by blowing cold compressed air on them!

I can assure you this was no trick... Tom observed it. At the start, the whole tube was dull.