Sir David B. McNee, Q.P.M., could have been sent from the casting office to play the role of the head of Scotland Yard -- a big, bluff, hearty man with an air of authority.

Reminded you of Jack Hawkins in the screen role of Gideon, on of the most famous of the fictional Scotland Yard detectives.

"Gideon?" said a puzzled Sir David. "I've never heard about him. He's not on our roll of honor at Scotland Yard."

"Gideon? or was it Fabian? Anyways, he wasn't chief of Scotland Yard," said Chief Superintendent Bill Taylor, who is traveling with Sir David as his aide on a tour of American police stations to exchange information on crime-solving and prevention.

Last night Sir David and Lady McNee were guests at a dinner party at the International Club given by the Police Foundation, headed by Patrick Murphy, former chief of police in Washington, New York and Detroit. It must have been the safest place to be in town. Among nearly 100 guests were area chiefs, officials from the FBI, Justice Department, Drug Enforcement Administration and the Secret Service, and presidential counselor Ed Meese.

Sir David, who was awarded his Q.P.M. (Queen's Police Medal) in

Sir David, who was awarded his Q.P.M. (Queen's Police Medal) in 1975 and knighted in 1978, chose to exercise his right to remain silent when asked about firearms or the murder of Atlanta's black children. As for the Reagan administration's new task force on violent crime, he said Britian shares the same problem.

"We have a lot of violent crimes," Sir David said. "It impinges on people's lives -- a house broken into or someone molested on the street. We have reduced serious crime by targeting and concentrating our forces."

Scotland Yard, as symbolic as it has become in both real life and fiction, is just the name of a place -- the headquarters of the Metropolitian London police force. Sir David commands 24,000 officers and 15,000 people who handle support services.

With this staff, he is responsible for police protection of 7 1/2 million people in an 800-square-mile area of London and its environs -- except for one tiny section in Old London that takes care of itself.

"Call in the Yard," the provincial chief contables always say in British mysteries, and a Scotland Yard inspector or superintendant arrives to crack a puzzling case in a most civilized manner.

I'm afraid I'm going to shatter another illusion," Sir David said regretfully. "Those calls to Scotland Yard don't come so frequently since we regionalized our police forces."

For that reason, Sir David said he could offer no special knowledge of the Yorkshire Ripper case since it was handled by the chief constable of West Yorkshire.

West Britian had a half-million serious crimes last year, from stealing to murder, Chief Superintendent Taylor pointed out. But the homocide statistics are startling in number for another reason. Only 207 murders were reported in Britian last year. In 1978 in the United States, 18,714 murder victims were listed by the police -- a marked difference even when considering the differnce in population.

Sir David has been consulting with Murphy and others at the Police Foundation on problems of police training and efficiency. The foundation, a nonprofit group, was established in 1970 by the Ford foundation to foster improvement and innovation in police work.