Nick Hewer announces he is leaving The Apprentice

has decided to leave

after

on the hit BBC show. The PR expert, 70, said he thought it was the "

" to end his tenure, but said his departure was with "

". Nick has a long-standing relationship with Lord Sugar;

when Nick began promoting Alan's Amstrad brand.

© Photo: BBC

His exit was announced as he filmed the

, which will be screened on Sunday at 9pm. Viewers will see

and

fight it out for the chance to win a

for Lord Sugar. Nick has appeared on

since it began in 2005. He and

are tasked with keeping an eye on the candidates and giving feedback to Lord Sugar when he decides who to fire each week in the boardroom. Karren is the second advisor to work alongside Nick in the role, following

's departure in 2009.

Lord Sugar tweeted his response to Nick's announcement, saying, "It's with

from the apprentice. I thank him sincerely for the past 10 years." Explaining his departure in a statement, Nick said, "

and have decided that year 10 is the appropriate time. "

. Anyone can do what Karren and I have been doing, but

, and my stamina is not up to those long weeks."

© Photo: BBC

Nick – who hosts the Channel 4 show

– also paid tribute to the show's many candidates. "I've enjoyed being part of this wonderful television series for two reasons: firstly, because it's been fun and has opened up many unexpected opportunities for me, but more importantly, because

, teaching young people the basics of business – not in a classroom setting, but in a wonderfully entertaining format. "

– talented, creative and hardworking young people, all of whom are making a great success of their business."