Why did not UK assist Greece against Turks in 1919 war?

Greece had historical ties with UK. But no significant assistance by UK was provided to Greece during the war. As far as I know British Armies were already invading Istanbul and were close to the battle front.

It seems UK deliberately and indirectly left the country for Turks. What might be the reason behind this decision? Why did not UK help its Christian ally to obtain the West Anatolia?