Oh Bugger! How did you notice? Feel yourself elongating ?
The seat brackets were creaking more than usual (they all do that on this model) on the previous ride.
This time it felt like it wanted to shimmy, like a soft front tyre and lots of weight on the rear rack (you'd normally put heavy stuff on the lowrider first).
After stopping a couple of times and investigating suspension, headset, etc, I gave in and added more air to a tyre that didn't really need it. As I started off, slightly uphill, I felt the seat position shift in a manner that I interpreted as the rear shock coming apart. The rear shock had not come apart, the main tube had, and was bending under pedalling force.
It was just about ridable for a bit if I sat forward in the seat, to keep the break in compression, but after wheeling it for a couple of km the frame was sufficiently twisted that it was full wobblebike.
Oh dear...
Repairs are always possible. Aluminium? Case of whether you can be bothered.
This is actually steel (and interestingly no sign of corrosion at the break). I'm reluctant to go the repair route, on the basis that it's an obsolete model, and various suspension/drivetrain components are unobtanium and wearing out (it's currently sporting a piece of marine fuel hose as a drive-side idler). The simple solution would be to bag a low-spec second hand one with a sound frame and swap the parts over.
But I'm thinking the better solution, in the absence of war, famine or disability, would be a whole new bike with the Rohloff it really ought to have and current components, transfer over my custom cranks, lighting, etc. And reasonably expect another decade of use before I have to replace anything expensive. But you could probably buy a small flat in a rougher part of Blackpool for the going price...