It was to record those realities  for the service itself, as much as for the public  that Sir John Scarlett, then the MI6 chief, approved the approach to Mr. Hart Dyke as part of the centenary observances of “the service” in 2009. That milestone in MI6’s status as the Western world’s longest continuously operational intelligence service was also marked by an 800-page book, “MI6: The History of the Secret Intelligence Service,” published last year and based on access to the agency’s pre-1949 archive granted to Keith Jeffery, the author.

The watchword for both enterprises has been high caution, as befitting an organization that began stepping into the public domain only in the past 20 years. For decades, even its existence was secret; its chief’s identity was not publicly divulged until 1992. Sir John, who retired in 2009, was the first C  the service’s signature name for its boss  to have a public profile when he took the job, having previously served under Prime Minister Tony Blair as the government’s chief intelligence coordinator during the prelude to the invasion of Iraq in 2003.

Sir John, now a consultant to Morgan Stanley in London, said in a telephone interview that inviting a painter into the inner sanctums of the service was, in a sense, only an extension of a long-established practice of engaging with outsiders. “The service doesn’t live in a closed box,” he said. “People with special talents come in to help us all the time.”

Left unsaid was that Mr. Hart Dyke’s selection owed much to his record of having worked on other important projects. Before the MI6 commission, he spent weeks on combat deployment in Afghanistan with the Grenadier Guards, one of Britain’s crack army units, and traveled abroad on several official tours with Prince Charles.

The theme for the project, Mr. Hart Dyke said, was “to show what S.I.S. officers do without showing too much”  and that he was to do it at his own expense. The arrangement also stipulated that all the works be submitted for MI6 approval, a commitment that resulted in Mr. Hart Dyke’s having to remove some details from half a dozen works, leaving what he described as “holes” in the canvases. “I think the holes add to the sense of intrigue,” he said.

That the approach has succeeded is suggested by the sale of two-thirds of the works on the exhibition’s opening night, including “Waiting in the Hotel Room.” They fetched prices that ranged from $1,750 to $56,400. Prints of the works are also on sale. Some of the originals went to serving and retired MI6 officers; several of them, including Sir John, identified their favorite as the oil showing the agent lingering tensely at the hotel room window.

Sir John’s career included a stint in the mid-1980s as MI6’s station chief in Moscow. It was from there, in 1985, that Col. Oleg Gordievsky, a high-value mole in the K.G.B., was smuggled out of the Soviet Union to Finland in a hidden compartment in a British Embassy vehicle when he was on the verge of being unmasked. Perhaps dipping into that experience, Sir John said the hotel room painting had a special resonance for any intelligence officer who had kept a secret rendezvous.

“Almost everybody in the service, from me onwards, have recognized that scene, and experienced the tension it conveys,” he said.