Well the canonical example is Diana Athill who had a long and distinguished career at a literary editor for people Phillip Roth, John Updike, Margaret Atwood, Jack Kerouac and others, then retired at the age of 75 and started writing her own novels and memoirs and is considered one of the greatest writers in English of the 20th century. “After a funeral” is I think the one of hers I read and it’s amazing

https://en.wikipedia.org/wiki/Diana_Athill