“JOHN AND YOKO: A LOVE STORY,” Monday,...

“JOHN AND YOKO: A LOVE STORY,” Monday, 8 p.m. (4) (36) (39)--Imagine . . . there’s no television. It’s not easy, even if you try.

Then there would be no TV docudramas, and Americans would not expect truth about celebrities from their TV sets.

Imagine. . . .

Well, if Charles and Diana were worth two TV movies, John Lennon and Yoko Ono are certainly worth one. And for better or worse, this three-hour NBC movie is about to become their biography of record via a medium that touches more people in an evening than even best-selling authors do in a lifetime.

If Lennon was a significant influence on contemporary music as one of the Beatles, and Yoko Ono was a significant influence on him, doesn’t it follow that this account of their life together should also be significant?

Perhaps not, but it is highly watchable, if far too long.

Others will have to vouch for its authenticity, but it does play pretty well dramatically, thanks largely to look-alike performances by Mark McGann as John and especially Kim Miyori as Yoko. Although there are times when McGann flattens into a sort of Liverpoolian Leonard Zelig, Miyori’s Yoko is hidden surfaces and subtle shadings, suggesting a person as intriguingly off-center as her avant-garde art.

In fact, Yoko is far the more interesting of the two in this account, pictured here as Lennon’s backbone and the central influence on the social attitudes expressed in some of his later music.

The story, written and directed by Sandor Stern, begins with the couple’s meeting in 1966 and ends with Lennon’s murder in 1980 by Mark David Chapman. Stern has nicely avoided making the couple unflawed super characters, and also kicks a little dirt at Paul McCartney and George Harrison.

Otherwise, though, “John and Yoko” is exactly what it advertises, a tender romance, properly footnoted, but yielding few insights into the songs of Lennon and the Beatles or into the era that gave birth to their extraordinary success.

Good music, though.