For those too young to remember, the Guardian obituary by Christopher Hawtree describes them well:
The Henry Root Letters (1980) was a collection of correspondence between the supposedly retired wet-fish merchant, Root, whose clever if unhinged jottings to the great and the good, often enclosing small sums of money, elicited some wonderfully revealing responses. They were, of course, penned by Donaldson.From the obituary it is clear that there was a great deal more to Donaldson than Henry Root. He was joint producer of Beyond the Fringe, making much more out of it than the four performers, and enjoyed romances with the actress Sarah Miles and the singer Carly Simon.
And no writer could wish for a better epitaph than this, which comes from a note added to the obituary by Richard Milbank of his publishers Weidenfeld & Nicolson:
Willie's conduct as a writer, while always playful, somewhat belied his image of a chaotic and irregular life. He was respectful of deadlines, receptive to editorial suggestion and meticulously correct in matters of style and presentation.