"Because that's what Agatha knew, she freely admitted that she didn't know very much about ballistics. So if she starts writing about ballistics she would not be that much convincing," says Harkup who has penned a book on Agatha Christie.
In the 66 detective novels that Agatha penned in her prolific career, she poisoned more than 300 characters with 30 killer compounds that she used in a staggering array of creative methods.
The British author Christie, says Harkup, was equally good in her background research.
Christie used poison to kill her characters more often than any other murder method - with the poison itself being a central part of the novel - and her choice of deadly substances was far from random; the chemical and physiological characteristics of each poison provide vital clues to discovery of the murderer.
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Known as the "Queen of Crime Fiction," Christie's novels were very popular and some of them acted as inspiration for real life murderers.
However she admits that the best-selling crime fiction author can't be held responsible for gruesome crimes.
"Christie is also credited for saving lives. Knowledge is a good thing to have. But you can't hold the knowledge responsible for what an individual does with that."
"If media is an inspiration for murder then there would be
chaos. We can't watch 'Tom and Jerry' and start bashing each other. Most people recognise that this is fiction and where to draw the line," says Harkup who has completed a doctorate on her favourite chemicals, phosphines.
"It's been so nice to hear that Agatha Christie is so much popular in India. I knew she was popular but I had no idea that she was that much popular. I think she is so much more popular here than in the UK," she says.
Harkup says that despite being a chemist, she wrote her book in such a way that the general readers can understand it.
"My job is to make things simpler for readers. I know scientists can make things look difficult. I try to make it sensible for so many people reading the book. Logical steps, use of analogy, I try to use examples so anyone can relate to it."
"I think there is human fascination with the darker side of life, because all of horrible things are happening in fiction and not in real life. It is the general obsession with all these things like rape and murder and knowing that 'you are safe' and is happening to someone else and not to you," she adds.
She opines that Crime Writers' Festival must return next year.
"Crime writing is the only genre of literature fest in India, I would encourage it, because there are so many Indian authors who write crime fiction. Adding to that, she says Anuja Chauhan is her favourite author.
Harkup wrote "A is for Arsenic: the poisons of Agatha Christie" where she analysed 14 poisons, in alphabetical order used by Christie in her fiction. The book has been published as part of the 125th anniversary celebration of Christie's birth.