He started his long career in practical horticulture when he was sixteen and wrote his first book mainly in RAF hospitals before being invalided out on D-Day.

Whilst researching a book called Russian Comfrey, Hills discovered that this common plant was introduced in the nineteenth century by Henry Doubleday (1810–1902), a Quaker smallholder who was so intrigued by its possibilities that he devoted the rest of his life to popularising it.

Persistent lobbying of government eventually resulted in the world's first vegetable gene bank where seed was deep frozen and stored forever.

Hills appeared on television, lectured and broadcast on the radio in Great Britain, the US, South Africa, Belgium, France, Australia and New Zealand.

HDRA hosted the 1987 television series on organic gardening All Muck and Magic which became so popular that it was one of Channel 4's top five programmes, attracting 3.5 million viewers a week.