Sir Alan Sugar’s advisor, Margaret Mountford, has quit the show after five years.

The Northern Irish corporate lawyer acts as Sir Alan’s eyes and ears on the show, as she and Nick Hewer shadow teams of candidates and report back on their performance throughout the tasks.

The Sun reports that Mountford will quit after this years series ends in order to finish her doctorate on ancient Egyptian manuscripts.

A show insider told the newspaper: “This will come as a big blow to Sir Alan and the millions of viewers.

“Margaret and Nick have almost as big a following as Sir Alan.

“She is very sad to be leaving but she feels the time is right.

“When she started I don’t think she had any idea just how popular it would become.”

The source added: “She has enjoyed every minute but it is very hard work and she wants to go out on a high.

“Margaret has told Sir Alan, who understands her reasons and thanked her for her hard work.”