Plath, the poet whose verse spearheaded an emerging literary voice for women in the Sixties, took her own life in 1963. For his sculpture, which he was unveiling at Smith College this weekend, Dimbleby has taken as his theme one of her best-known poems, "Lady Lazarus", with its memorable lines: "Dying/ Is an art, like everything else./ I do it exceptionally well."
As in The Bell Jar, Plath's semi-autobiographical novel, the poem chronicles with bitter irony her various suicide attempts ("This is Number Three"). In doing so, it also prefigures her final attempt, which she executed "exceptionally well" by entering a gas oven head first.
The memorial to Plath, who studied both at Smith, then the leading US women's college, and at Cambridge University, where she met Ted Hughes, the present Poet Laureate, whom she later married, has been commissioned by her friends Elizabeth Sigmund and Clarissa Roche.
This weekend, as Dimbleby unveils his maquette model for the sculpture at Smith's graduation day, they will appeal to Plath's contemporaries from the class of '53 for funds to build a life-size version for the university's library.
The subject of Plath and memorials has been controversial in the past. In the Seventies her devotees intermittently defaced the headstone at her British grave to scrub out the "Hughes" from "Sylvia Plath-Hughes", in the belief that Ted Hughes stifled and maltreated her.
Dimbleby has not consulted Hughes about this latest project, but says the wording on his sculpture will simply read "Sylvia Plath", with a few lines from "Lady Lazarus".
He says he is particularly fascinated by Plath's ability to "face the failure", something that strikes a chord with the youngest son of the eminent broadcaster Richard Dimbleby and younger brother of David and Jonathan.
After an election-time television glut of his siblings, 50-year-old Nicholas is almost regretful at putting another Dimbleby in the public eye. "There has been a surfeit of Dimblebys lately," he says shyly.
He goes on, in the familiar Dimbleby tones more usually employed in questioning Cabinet ministers: "It's difficult if you come from a family of people who succeed in a very apparent way. Of course, everyone succeeds or fails, but if you don't succeed in an obvious way in a family of manifest success you look like a failure.
"Success does become expected in some way. It can become a case of how does one impress one's parents, whether they are alive or dead. Luckily my father felt that personal fulfilment was the most important thing, so art was an acceptable career.
"I wasn't under pressure to go into broadcasting. But you do always have to think: `Am I doing this to join in or should I be doing something more modest but more fulfilling?'"
He is anxious not to put his own sons and daughters - Joe, Edmund, Maisie and Grace - under any pressure to succeed.
"In a way my children suffer from not being pushed enough," he says. "But then there's Maisie, who has applied to Rada, dreaming of success and driven by a need for applause.
"It just seems to be genetic. My brother Jonathan was very shy when he was younger, but it seems he has now greatly taken to performing."
Nicholas Dimbleby is passionate about Sylvia Plath. "She lived life at the edge, but she was always able to be coherent," he says. "I know some men find her sometimes too shrill or too intense, going too near that edge, but to me she is just at that point of coherence and incoherence." He laughs and quotes from "Lady Lazarus": "I eat men like air".
"People think she spent her whole life in depression or in institutions," he continues. "In fact she was very good at living life. She lived on the surface and right underneath at the same time ..." The sculptor cuts himself off with a very un-Dimbleby-like self-consciousness. "But then you don't want a lecture from me on Sylvia Plath," he says. "I just get a bit carried away."
He says he is "very conscious of the fact that people are interested in me as a Dimbleby rather than as a sculptor". But, he adds: "Anything that can help bring attention or funding to sculpture, the thing I love, has to be good. There is a constant problem for art in that the people who have the ideas and the vision aren't usually the ones with the organising capabilities or the money."
Last week he won the commission for a Duke Ellington statue for London's Soho Square with an elegant maquette of the jazz musician standing by his piano. The man behind the project is Peter Boizot, Pizza Express chairman and jazz lover. Despite the interest of big business, fundraising for the statue is only just beginning. Meanwhile, unless her college contemporaries put their hands in their pockets this weekend, Sylvia Plath will remain just over a foot tall instead of the bronze amazon in the mind's eye of her sculptor.
Although Nicholas Dimbleby may dream of the million-pound broadcasting budgets his older brothers command, he is content with his choices.
"I often think," he says, "that my brothers must be envious of me. My sculptures go off to the clients and I am left with my plaster casts, my ghosts. But when my brothers go on television in front of millions of viewers, the cameras stop and that's it. My work goes on sustaining me, but theirs is gone with the sunrise."
From Lady Lazarus by Sylvia Plath
The first time it happened I was ten.
It was an accident.
The second time I meant
To last it out and not come back at all.
I rocked shut
As a seashell.
They had to call and call
And pick the worms off me like sticky pearls.
Is an art, like everything else.
I do it exceptionally well.
I do it so it feels like hell
I do it so it feels real.
I guess you could say I've a call ...
Reprinted from Ariel, courtesy of Faber and FaberReuse content