Historian Chris Collins says the 1981 Thatcher files reveal a prime minister under pressure but "not cracking".
The year - which saw the July wedding of the Prince of Wales and Lady Diana Spencer - was dominated by the failing economy and riots which broke out in several cities during the summer.
Thatcher also had to contend with the prospect of a split in Conservative ranks. Files suggest fears that a "gang of 25" Conservative dissidents may have been contemplating joining the Social Democratic Party.
But Collins, who works for the Margaret Thatcher Foundation, says papers suggest the prime minister was coping.
"Nineteen eighty-one was the gravest year of the Thatcher administration in some respects," he said.
"Riots. The economy was in trouble. There were close to three million out of work by the end of the year."
He added: "You can see the stresses she was under but she is not cracking."