Unidentified caterpillar

Unidentified caterpillar

Observation - Unidentified caterpillar. Description: Large green caterpillar that munched its way up and down my beautiful verbascum for a week then disappeared. Third pic gives an idea of scale and shows last remaining flower on verbascum, all the rest had been chomped. Any ideas what it could be?

Large green caterpillar that munched its way up and down my beautiful verbascum for a week then disappeared. Third pic gives an idea of scale and shows last remaining flower on verbascum, all the rest had been chomped. Any ideas what it could be?