In a statement released today, Coworth Park confirmed that Campbell, who having established the hotel's food and beverage offering when it opened, moved from a full time to a consultancy role in April, would end his contract on 30 November.
General manager Zoe Jenkins said: "We would like to thank John for all of his hard work and tremendous contribution to the launch of Coworth Park, and wish him well for the future."
Campbell, who joined the Dorchester Collection hotel in 2009 from the Vineyard at Stockcross, said it was time to 'branch out and explore new projects'.
"I am proud to have been part of the creation of Coworth Park, it is a stunning property with a great team and I have every confidence in the future of the food and beverage operation," he added.
A message from Campbell's PA following the news said Campbell had some 'exciting and promising opportunities ahead', details of which would be announced in due course.
"In addition to these new ventures, John will continue to work closely with Baxter Storey, and in conjunction with the publication of the much acclaimed Practical Cookery books.
The fine-dining restaurant at Coworth Park, awarded its first Michelin star this year, will continue to operate under the direction of executive chef Chris Meredith, formerly of The Samling and Gilpin Lodge.
The hotel expects to make a 'further announcement' on new members of the kitchen soon. Peter Eaton and Olly Rouse (both pictured with Campbell) who joined with Campbell, both left the hotel earlier this year.