Did Margaret thatcher do a geneology search on her self?

She wasn't the sort of person who cared much about ancestry.

But there was a persistent local rumour that her mother Beatrice was illegitimate. Beatrice's mother is known to have started-off working in domestic service at several of the local stately homes, almost certainly including Belton House, home of Harry Cust, editor of the Pall Mall Gazette. If the rumours were true, it would explain the physical resemblance between the handsome blond Cust and the handsome blonde Margaret Thatcher.

Cust was also identified - virtually beyond question - as the natural father of Lady Diana Cooper, who denied it for at least sixty years, but then got bored and told an astonished interviewer that she didn't mind him publishing it. In her old age, she would refer to Margaret Thatcher as 'my niece'.