The Mote in Gordon's Eye.

Be careful, Mr Brown,
as you unleash your glowering frown
and mutter about certain playing fields.
A minister's son might
consider motes and eyes affecting sight
and better consider the stick he wields
to beat up opposition.

Yes, take care, Mr Brown:
for what you don't seem to get is
your modern party was born
on the playing fields of Fettes.