In message , spindrift
writes

Hi,

Does anyone know what this plant is please that has appeared in my
garden. The underside of the leaves is very prickly and the top of the
leaf has what looks like prickly warts but not on every leaf. Apologies
for the vague description.

Try googling for images of Picris echioides (bristly oxtounge) and see
whether that's a match.
--
Stewart Robert Hinsley