Question: Joe gray was technical advisor to an actor who was considered "maybe the greatest actor who ever appeared in front of a camera" by who? 

Context paragraphs:
Dale Dye: Captain Dale Adam Dye Jr., USMC (Ret.)  (born October 8, 1944) is an American actor, technical advisor, radio personality and writer.  A decorated Marine veteran of the Vietnam War, Dye is the founder and head of Warriors, Inc., a technical advisory company specializing in portraying realistic military action in Hollywood films.  Dye has also offered his expertise to television, such as the HBO miniseries "Band of Brothers" and "The Pacific", and video games, including the "Medal of Honor" series.

Technical advisor: A technical advisor is an individual who is an expert in a particular field of knowledge, hired to provide detailed information and advice to people working in that field.  For example, a construction company might hire a technical expert in fluid dynamics to advise them if seeking to move a small water course or a company operating in adventure education will frequently hire technical experts to ensure that their policies and procedures are robust enough to handle the hazards they are going to face.

Technical Chamber of Greece: The Technical Chamber of Greece (Greek: Τεχνικό Επιμελητήριο Ελλάδας ) (TEE-TCG) is the Greek professional organization that serves as the official technical advisor of the Greek state and is responsible for awarding professional licences to all practicing engineers in Greece.  It is a public legal entity with elected administration, supervised by the Hellenic Ministry of Environment, Physical Planning and Public Works.  The Technical Chamber of Greece is a member of the European Council of Applied Sciences and Engineering.

David Henke: David Richard Henke is an American entrepreneur, businessman, and technical advisor.  He served as the Senior vice president (SVP) of Engineering and Operations for LinkedIn, a professional social networking website, from 2009 to 2013.  He currently serves as a technical advisor for Elementum SCM, and is on the board of Turn, as well as Sean Parker's political advocacy startup, Brigade Media.

Angels One Five: Angels One Five is a 1952 British film directed by George More O'Ferrall, and starring Jack Hawkins, Michael Denison, Dulcie Gray, John Gregson, Cyril Raymond and Veronica Hurst.  Based on the book "What Are Your Angels Now?"  by Pelham Groom (who was also technical advisor to the film under his full title of W/Cdr.  A. J. C. Pelham Groom), the plot centres on a young fighter pilot immediately before and during the Battle of Britain in the Second World War.  Some scenes in the film were shot at RAF Uxbridge, home to a wartime operations room.

Akira Kōdate: Akira Kōdate (高達秋良、こうだて・あきら) was born in Kanagawa District, Japan on 6 October 1925.  He is an engineer and a Japanese business manager, considered one of the greatest international experts in R&D and production management, as well as a master of lean thinking-related methodologies.  Since 1953, he has been working as a consultant with the Japan Management Association (JMA) and JMA Consultants Inc, where he works as a principal consultant and technical advisor.

Mack Gray: Mack Gray (11 December 1905 in Brooklyn, New York, USA – 17 January 1981 in Beverly Hills, California) was an American actor who was the brother of Joe Gray and great-uncle of Jon Abrahams.  He was given the nickname "Killer" by Carole Lombard due to his roles in films as a tough guy.  Longtime friend and confidant of George Raft, Dean Martin, and Frank Sinatra.

Robert Dover (equestrian): Robert Jeffrey Dover (born June 7, 1956) is an American equestrian who has had international success in the sport of dressage.  Riding from the age of 13, he began specializing in dressage at age 19 and competed in his first Olympics in 1984.  He competed in every summer Games between 1984 and 2004, winning four team bronze medals.  He also took a team bronze at the 1994 World Equestrian Games.  Dover is the most honored dressage rider in the United States, and has been inducted to the United States Dressage Federation Hall of Fame.  Outside of competition, Dover founded the Equestrian Aid Foundation in 1996 to assist others in the equestrian world, and hosted a TV show that searched for the next dressage star.  From late 2009 to early 2011, Dover served as the Technical/Coach Advisor for the Canadian national dressage team.  In April 2013, Dover was named Technical Advisor/Chef d'Equipe for the US national dressage team.

James Cagney: James Francis "Jimmy" Cagney Jr. (July 17, 1899March 30, 1986) was an American actor and dancer, both on stage and in film, though he had his greatest impact in film.  Known for his consistently energetic performances, distinctive vocal style, and deadpan comic timing, he won acclaim and major awards for a wide variety of performances.  He is best remembered for playing multifaceted tough guys in movies such as "The Public Enemy" (1931), "Taxi! " (1932), "Angels with Dirty Faces" (1938), and "White Heat" (1949), and was typecast or limited by this view earlier in his career.  In 1999, the American Film Institute ranked him eighth among its list of greatest male stars of Classic Hollywood Cinema.  Orson Welles said of Cagney, "[he was] maybe the greatest actor who ever appeared in front of a camera", and Stanley Kubrick considered him to be one of the best actors of all time.

Joe Gray (actor): Joe Gray (May 5, 1912 – March 15, 1971) was an American boxer, actor and stuntman who made appearances in over 110 films in numerous uncredited roles, including 10 of Frank Sinatra's films and 32 of Dean Martin's films.  He was a technical adviser on boxing films for John Garfield, Elvis Presley, Jeff Chandler, James Cagney, George Raft, Tony Curtis, and Kirk Douglas, among others.

Supporting paragraphs: Joe Gray (actor) James Cagney
Answer: Orson Welles