'I have an attraction to monsters," declares Martin Sherman. The 71-year-old playwright says this partly by way of playful confession.
Can he reveal which monsters?
"I can't," he responds with a wry smile, as if naming names would disclose too much about himself.
We are sitting in a wine bar behind the Wyndham's Theatre in London. By coincidence, that is the venue which in 2003 hosted Sherman's version of Luigi Pirandello's strange, convention-busting play, Absolutely (perhaps), which was directed by the legendary Italian filmmaker Franco Zefferelli and which starred the equally legendary Joan Plowright, aka Lady Olivier.
The tall, Philadelphia-born septuagenarian cuts a youthful figure in a green bomber jacket and Castro-style army cap. There is, it seems, plenty of energy for more scripts. Just opened is his latest West End play, which is why we are talking about monsters.
So yes, I have taken the conspiracy theories about Onassis as a given
After mixed reviews at Chichester earlier this year Sherman has changed the name from Aristo, which could be about anything from aristocrats to philosophy, to Onassis, which can only be about the Greek magnate who married President John F Kennedy's widow, Jackie, and, according to Sherman's play and Peter Evans's book, Nemesis, on which it is based, also bankrolled the assassination of the president's brother, Bobby.
The world is not short of conspiracy theories surrounding Kennedy assassinations, but Sherman has no doubts. "I completely believed in the book," he says in his softened American accent, the product of living in London for 30 years. "In most of these kind of books the sources are shadowy and there is a lot of hearsay and rumour. So the first thing I did when I got the book was to turn to look at the sources at the back. And they are impeccable. So yes, I have taken the theories as a given."
(The most startling one is that Onassis, who owned the Greek national airline, Olympia Airways, paid protection money to the PLO so that his planes would not be hijacked.)
You have to be attracted to a character to write about him, is Sherman's point about monsters. There is much to dislike about Onassis, but you do not gain real power by being nice. Plus, Onassis was Greek and Sherman likes Greece. He has a house there, as well as the Bayswater apartment into which he moved in 1980 after his most successful play, Bent, opened on Broadway.
It took a Jew to write a play about the Holocaust that highlighted the persecution of non-Jews. Set in pre-war Berlin on the cusp of the Nazi's anti-gay purge, and then in a concentration camp, Bent revealed the extent to which gay people suffered under the Nazis. Twenty years later Sherman turned to the Holocaust again with his one-woman play, Rose, which opened at the National Theatre and then moved to New York.
In Rose, his 80-year-old heroine declares that "Judaism's greatest contribution to mankind was asking questions that cannot be answered".
"It's my most popular play in Europe," says Sherman.
It has also been called anti-Israel, I point out. And Olympia Dukakis, the actress who created the role and who still performs it, recently said that some members of the audience have shouted that it is antisemitic. Sherman is unfazed.
"I guess because Olympia is not Jewish, she doesn't completely realise the extent to which Jews attack each other," he says, digging into his avocado salad.
"There were some people in New York who called it anti-Israel, which is not the same thing. What amazed me was how few there were. But I wanted that to happen. I knew what I was writing." Though the play remains popular in Israel, Sherman says that it has received its share of criticism there, too.
"The Israelis weren't upset by Yiddish culture being destroyed. They were upset by my saying it shouldn't be destroyed. They see Yiddish culture as the culture of people who gave up; who didn't fight back. They're embarrassed by it. They see it as a culture that was suicidal, where, in fact, the opposite is true. I think that European Jewish culture found itself in a situation where there was no way out. There is a way out for the Israelis, but they don't choose those options. They choose the suicidal option."
This is a view, Sherman is keen to point out, made out of deep affection for Israel. He goes there often and many of the people he loves there remind him of his own family.
Like the fictional Rose, Sherman's parents were born in Ukraine and emigrated to the US, where his father managed to become an attorney. "I'm still trying to understand how that happened," he says. "My father's parents were peasants. Three of their kids were born in Russia. My uncle couldn't afford to go to medical school so he became a podiatrist, my aunt became a piano teacher, and my father became a lawyer - criminal and divorce. His clients were very poor. He didn't know any law. It took him six times to pass his bar exam, but he had a courtroom technique that was unparalleled. He could always produce reasonable doubt in a jury. And the youngest brother, who was born in America, is the joke. He's the nuclear scientist."
The Sherman canon includes a play about the dancer Isadora Duncan, the film Mrs Henderson Presents, about a wartime strip club, and a second play featuring gay characters, called Passing By. One is tempted to suggest that homosexuality is Sherman's most fertile subject matter. He disagrees.
"Oh, I think I write about people who are marginalised from society," he says. People such as Jews, or gays, and even one character who was born in Turkey and so marginalised by Greek society in his early years - a certain Mr Onassis.