The Sun remained loyal to Thatcher right up to her resignation in November 1990, despite the party's fall in popularity over the previous year following the introduction of the Poll tax (officially known as the Community Charge). This change to the way local government is funded was vociferously supported by the newspaper, despite widespread opposition, (some from Conservative MPs), which is seen as having contributed to Thatcher's own downfall. The tax was quickly repealed by her successor John Major, whom The Sun initially supported enthusiastically, believing he was a radical Thatcherite despite the economy having entered recession at this time.
When did Margaret Thatcher leave office? (If the question is unanswerable, say "unanswerable")
November 1990