Clive George wrote:

Friends with a thorn adventure had their forks fail on them at the
steerer/crown. These are the funny thorn two-plate ones.

Fortunately the failure mode was the steerer tube cracking/becoming detached
from the bottom plate, giving a horrible wobble but no actual crash.

Funnily enough they don't trust adventure forks any more, but will give the
stronger discovery ones a go. I reckon this is a fair replacement - I
wouldn't expect any rigid forks on a touring bike to fail without a crash,
since they are such a safety critical item.

Mr Thorn has offered the discovery forks as a replacement for 50 quid
extra - I think he should give them for free.

I take it that a pair of replacement Adventure forks would have been
free under the lifetime warranty? I suppose it's fair to charge the
difference in price if this is the case, but I'd be interested in how
seriously he's taking the failure of the original ones. It sounds like
poor brazing to me, since really slender steel forks can stand up
perfectly well to rough roads.