English conservationist David Bellamy, best known in New Zealand for his impassioned campaign against Old Man's Beard, has died aged 86.

The British Conservation Foundation, of which Bellamy was co-founder and president, said in a statement to The Guardian he died yesterday.

In the late 80s, Bellamy, already a well-known broadcaster in the UK, fronted a campaign for the New Zealand Department of Conservation (DoC) to eradicate the noxious week Old Man's Beard.

"Old Man's Beard must go!" he memorably pronounced in a series of TV ads.

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He also presented a series about New Zealand's native flora and fauna, Moa's Ark, which aired in 1990, and was the celebrity face of Woolmark carpet.

Born in London, Bellamy was a botany teacher at Durham University before launching his television career in the late 1960s.

He was recognisable for his full bushy beard and distinctive voice, characterised by rhotacism, or difficulty pronouncing the letter "r".