MAN FROM U.N.C.L.E. and NCIS star DAVID McCALLUM’s secret sorrow.

Shooting to stardom as Russkie secret agent Ilya Kurakin on hit 1960s tele-series The Man from UNCLE, McCallum had more than his ups and down both personally and professionally.

Despite all the homicides he keeps count of on the NCIS as Dr. Donald "Ducky" Mallard, only one death haunts him – the tragic drug OD of his adopted son JASON in 1969.

"I wasn’t there for him during the time leading up to his death," McCallum admitted.

"I lost touch with and control of what was happening there."

David and his then-wife actress JILL IRELAND had adopted Jason but soon after divorcing Jill after she dumped him for his GREAT ESCAPE costar CHARLES BRONSON, "I lost touch with and control of what was happening there.

"Jason got in with a certain type of people within show business and there was a drug culture going on. Despite the best efforts of Jill, he couldn’t be saved.

"He became part of that drug culture and it killed him."

Despite having had two other boys with Jill and two more children with second wife Katherine Carpenter, McCallum admitted that Jason who died at 26 held a special place in his heart.

"Jason came from left field," David recalled. "You love your own children, of course you do, but you have a rough idea what to expect because they are genetically similar to you.

"That wasn’t the case with Jason. He surprised and delighted us."