Mountford will now concentrate solely on her PhD in papyrology, leaving Sir Alan Sugar to find a new assistant for the show's sixth run next year. Writing in The Daily Telegraph, she confirmed: "This will be my last series on The Apprentice. I have really enjoyed making the series and it will be a real wrench to say goodbye.

"But making The Apprentice takes up a large chunk of time each year, and that's time I could, indeed should, be spending on my studies. I am working on a PhD in papyrology at University College London, studying documents found in Egypt and written in ancient Greek.

"I have not made nearly as much progress as I would like over the last few years - and I want to finish my degree before I need a Zimmer frame to get up on the platform to receive it."

Responding to the news, Sugar commented: "Margaret has been a highly regarded colleague and friend for over 25 years. Five years ago she agreed to put her studies on hold for the first series. None of us expected the show to be such a big hit, but now, five years later, she really wants to finish her Masters.

"We will miss her, but I respect her wishes and want to take this opportunity to thank her for the great contribution she has made to the series and of course wish her the best of luck with her studies."