diametrically

Separated by a diameter, on exactly the opposite side.

Absolutely (in opposition).

"I do not see that we are at all called upon to pay so costly a compliment to society, as to assume a character diametrically opposed to our real one,—to utter sentiments we secretly disbelieve,—and to be as angry with our better nature for bursting from restraint, as at other times with our own inferior nature for refusing to submit to it.

The distinctness of London has led many to clamor for the capital to pursue its own policies, especially on immigration. The British prime minister, David Cameron, is a Conservative. So is the mayor of London, Boris Johnson. But they have diametrically opposed views on immigration.