With a PoD of 1865, have Britain be just another Great Power rather than the strongest, or a mere shell of what they were OTL by 1900.
Preferable with India lost, Canada taken, Britain bankrupt or deeply in debt, Ireland and/or the Boers having had a serious rebellion, key areas like Gibraltar/Malta/Suez taken, Central Asia under Russia influence, and Britain bested by multiple other powers directly.