The TV star, 63, was cast as a quizzer on the ITV show in 2010.
Show producer Sue Allison has now told how Hegerty stood out when she wrote in saying that she had what it took to be a Chaser.
Speaking on the TV Show and Tell podcast, she said: “For the series I really wanted the third Chaser to be a woman, a strong woman who could hold her own and who would be completely herself.
“That was quite a hard task. I remember that we saw quite a lot of people. There were really good quizzers on the circuit, obviously that was the most important thing first and foremost."
Allison said that the team met with plenty of great quizzers but that quite often they were “just a bit too nice”.
"When we got a letter from Anne, she wrote into the team and said something like she, 'realised what kind of character you needed to be' because she’d seen the pilot series,” she said.
"And she realised you needed to be quite tough, and was the fact that she'd once chased off a couple of muggers the kind of thing that we were looking for."
She went on: "I remember getting this letter and reading it and thinking, 'Come on, come on, be as good as you sound’ and she was."
Hegerty has now been on the popular programme - which is hosted by Bradley Walsh – for 12 years, and is known as The Governess.
She also appears on spin-offs such as Beat The Chasers and in 2018 was a contestant on I’m A Celebrity… Get Me Out Of Here!
Watch: Anne Hegerty is a distant relative of the Queen