Celebrity chef Gordon Ramsay has told a High Court judge that he reacted with "shock and horror" when he made the "devastating" discovery that his wife Tana's father used a ghost writer machine to "forge" his signature.

Ramsay is claiming the machine was used without his knowledge to sign him up for the £640,000-a-year annual rent for the historic York & Albany pub near Regent's Park in London.

Ramsay is seeking a declaration that the guarantee does not bind him because his signature "was not lawfully authorised" when the 25-year lease was signed in 2007.

The chef says for a number of years he worked with his father-in-law, Christopher Hutcheson, who acted as his business manager for his group of companies.

He told Chancery judge Mr Justice Morgan his "deep and extensive trust in Hutcheson was entirely misplaced" and his father-in-law defrauded him and the group "of hundreds of thousands of pounds."

In October 2010, Mr Hutcheson was "summarily dismissed from the group".

As Ramsay was "piecing his business back together", his solicitors discovered that his signature had appeared on a personal guarantee in the lease for the York & Albany.

Ramsay told the court discovering the existence of the lease guarantee was "a shock - a devastation".

He said: "The company is still in the hook for the lease, and what was devastating for my wife and I was that we were guaranteeing it until 2033."

He added: "There were many horrific discoveries because I can recognise my signature and pinpoint one forged by machine."

The judge was told a key issue in the case was whether Mr Hutcheson was authorised, while managing the Ramsay group businesses, to use a "ghost writer" machine which he had obtained and which was used to sign Ramsay's name on the personal guarantee.

Film director Gary Love, who owns the York & Albany, has described Ramsay's allegation as an "absurd" attempt to wriggle out of his rental commitments.

Mr Love is represented in court and opposing Ramsay's application for a declaration that he is not bound by the guarantee.

Gordon Ramsay Holdings (GRH) won a bidding war to secure the 160-year-old building in the exclusive area of Regent's Park, north London.

The Independent reported that this pushed the rent far higher than the market rate, and Ramsay has since turned the pub into an upmarket restaurant, bar and hotel.

Ramsay is submitting to the court during a six-day hearing at which he will give evidence that he had agreed to the use of the ghost writer, which electronically replicates a signature using a fountain pen or ballpoint.

But he had done so "for purposes of merchandising material only".

However, Mr Hutcheson had "used the ghost writer far more widely than that, using it to sign various contracts in (Ramsay's) name".

Ramsay maintains Mr Hutcheson also used it to sign the York & Albany personal guarantee or loan, even though the chef had not authorised anyone to sign it on his behalf.

Giving evidence to the court, Ramsay said that between six and nine months after Mr Hutcheson was "removed from the business" in 2010, "it was discovered then that the lease was signed by the ghost machine".

He said it was discovered that "there were several documents that had been forged".

Cross-examined by Romie Tager QC, for Mr Love, the chef said he could not remember exactly which documents.

He said he and his wife were then "going through a very difficult time", telling the court that "there were several emails that were hacked so it is hard to categorise exactly when and what we discovered".

He said his father-in-law "never had permission" to sign any deal "via a ghost machine".