From 1966, Yallop wrote for several series, including
Orlando,
Crown Court,
The Rolf Harris Show,
Doctor on the Go, and
Minder. He was also one of the co-authors of
Graham Chapman's 1980
autobiography, ''
A Liar's Autobiography (Volume VI)''. In 1989, Yallop was fired as a
scriptwriter for
EastEnders when he proposed killing some of the characters with an
IRA bomb. He successfully sued the BBC for
breach of contract. He continued writing for television up until 2010, with his last series being 1995's
An Independent Man. He wrote the script for the 1980 docudrama
Beyond Reasonable Doubt (based on his own book), the screenplay for the 1990 film
Chicago Joe and the Showgirl, and the 2007 television film
The Marchioness Disaster. In the 2000s, he appeared in episodes of true crime TV series such as ''
History's Mysteries, Revealed
and Real Crime''. In 1971, his first book, about the
Derek Bentley case, was published. He wrote an additional nine non-fiction books, and one work of fiction. His best-known book, ''In God's Name: An Investigation Into the Murder of Pope John Paul I
(1984), posited that Pope John Paul I, who was found dead in his chambers soon after becoming pope in 1978, had been poisoned by Masons who had infiltrated the Vatican and the Vatican Bank. Reviewers, and the Roman Catholic Church, dismissed the book as groundless conspiracy theory. The book made the New York Times'' Best Seller list for 15 weeks, was translated into multiple languages, and was repeatedly reprinted, selling over six million copies. ==Personal life and death==