In message ,
newshound writes

Seamed pipe is a post-victorian pre-plastic replacement for cast iron.
Galvanized IIRC. Also found in industrial / farming properties, cheaper
and much lighter than CI so easier to install in longer lengths.

Thanks for that. Not something I have seen before, and what you say
certainly fits. Now repaired, and waiting for overnight rain to ensure
it all works!
--
Graeme