Peter O'Donnell was born on 11 April 1920 in Lewisham, London, UK. He was interested in writing as a child, and began writing professionally at the age of 16. During World War II he served in the Royal Signals Corps, and was stationed in Persia, Syria, Egypt, the Western Desert, Italy, and Greece.
After the war, he worked as a comic strip writer, and scripted the Daily Express adaptation of the James Bond novel Dr. No. He was most famous for inventing the character Modesty Blaise, an undercover agent who first appeared in comic strips in 1963. In 1965, he published his first novel, Modesty Blaise, which was based on the screenplay he had written for the motion picture of the same name. He also wrote short stories, plays, television and film scripts, and nine romance novels published under the pseudonym Madeleine Brent. In 1978, his novel Merlin's Keep won the Romantic Novel of the Year Award by the Romantic Novelists' Association.
In 2001, he retired from writing. He passed away on 03 May 2010.