Oxford's lexicographers, pointing out that -izo is found in late Latin too, spell nearly all -ise words in -ize.

ECONOMIST: Johnson: Don't shoot the pian-ist | The

In practice, British English today tends to use -ise, while Americans write -ize.

ECONOMIST: Johnson: Don't shoot the pian-ist | The

Why does Oxford, as in the old SOD, list words ending in -ise as variants of the same word spelt with -ize?

ECONOMIST: Johnson