Terf, which stands for trans exclusionary radical feminist, is generally used as a derogatory term to describe those who believe that “identifying” as a woman is not the same as being born a woman. It can also be used to refer to people who are deemed to hold “transphobic” views.

Prof Stock, who has received death threats from pro-transgender activists, has been advised by the police to have CCTV installed at her front door and put a marker on her phone so that if she dials 999 there is an automatic call-out to her house.

She said she felt “vulnerable”, adding that the police implied she would need security guards to accompany her around the university campus.

‘Dissent, disagreement and debate are fundamental to any democratic society’

Michelle Donelan, the universities minister, has said it is “unacceptable” that Prof Stock is having to be supported by the police following threats to her physical safety.

“Dissent, disagreement, debate and peaceful protest are fundamental to any democratic society,” Ms Donelan said on Twitter. “Physical intimidation or threats against those with different views is always unacceptable and action must be taken against the perpetrators.”

A University of Sussex spokesman said they were “extremely concerned” that a member of the staff was being harassed, adding that they had taken “immediate action” in response.

They added: “As a university community, we must be able to have complex discussions without bullying or harassment. We will always take swift action when this occurs.”

Waterstones said that both Bindel’s and Prof Stock’s books are being treated “like any other”. 

A spokesman said that their books are “available in many Waterstones shops and at waterstones.com, with stockholding reflecting current demand”. 

They added: “Some individual shops will have sold out, as is always the case with individual titles. They are then reordered, with newly arrived stock unpacked in the stock rooms and subsequently shelved when booksellers have the opportunity. Shelves and tables are independently curated by booksellers in each of our  bookshops. 

“With all the new autumn publishing arriving in our shops table display space is limited, with most titles being shelved in the appropriate sections. In short, both books are being treated as any other, with higher or lower sales in each shop according to customer interest.”