ILR rules says
ILR, also known as settlement, is permission to remain in the UK without any time
restrictions on the length of stay. It is not the same as naturalisation as a British citizen and
may, in specific circumstances, be ceased or invalidated. For example:
if a fraudulent application is uncovered
if the person resides outside of the UK for more than two years, or
as a result of a criminal conviction that results in a Deportation Order coming into force.
read page 3 of UKBA rules
https://www.gov.uk/government/uploads/s ... 7.0EXT.pdf