When he retired yesterday as director of the Royal Botanic Gardens he had, by common consent, made the venerable institution in south-west London the model botanic gardens for the new millennium.
Kew, of course, has long been famed, but Sir Ghillean has spent 11 years giving it a new sense of purpose as the world's leading centre for research into plants and their conservation.
He has taken a body that dates back to 1759 and still possesses noble trees from the 18th century, and given it a global reputation in molecular biology and plant genetics, the world's most advanced seed bank, and a 21st-century fund-raising machine that already brings in millions of pounds a year.
And he has done it while simultaneously grooming, expanding, restoring and enlivening the majestic 300 acres, with their long leafy vistas, their giant Victorian plant houses and their 40,000 varieties of flowers and trees.
He is 62 now, friendly but slightly formal. He is very fit (an enthusiastic squash player) and with his wife, Anne, a committed Christian, but more pertinently he is an expert on the flora of the Amazon rainforest, indeed, one of the world's foremost, having personally described more than 450 Amazonian plants new to science.
After a classically English start - brought up in Gloucestershire, educated at Malvern and Oxford - in his mid-twenties he departed, post-PhD, for the New York Botanical Garden in the Bronx, and remained there 25 years.
He rose, between annual Amazon expeditions - scorpion bites, malaria, canoes wrecked on river rapids - to the position of senior vice-president (in effect, deputy director) and as he did so adopted what is sometimes referred to as the United States' "can-do" attitude, but may simply be termed energy and purpose. He brought it back with him when he took up the reins at Kew in September 1988 and it was immediately visible in fund-raising, which in New York was seen as a vital and everyday task, but which at Kew was done hardly at all. That changed at once, with machinery set up that now enables Kew itself to provide one-third of its pounds 30m annual budget (the rest comes from government grant).
Kew avoided the retrenchment that afflicted many scientific institutions in the Nineties and has been able to expand continually. It has become a world leader in the science of molecular biology, the investigation of the relationships between plants through their DNA, their genetic code, rather than their appearance.
This yielded spectacular fruit last year when an international team led by Kew scientists produced a revolutionary new classification of all the world's plant families. They turned botany on its head by revealing numerous unsuspected relationships: the lotus, the sacred flower of the East, for example, was shown to be most closely related not to the water lily it so closely resembled, but to the plane tree of London's squares.
In conservation, Sir Ghillean has also made Kew a global leader with the pounds 80m Millennium Seed Bank at Wakehurst Place, Kew's Sussex outstation. This will be the world's greatest seed collection and aims to collect and store the seeds of 10 per cent of the world's 240,000 flowering plants by 2010 (including many of the most threatened) and 25 per cent by 2025.
By the end of this year it will already have the seeds of the 1442 native British wild plants, in the first instance of a country collecting and preserving the seeds of its entire flora.
Sir Ghillean has made countless additions to the grounds of Kew, adding new many new individual gardens - the Japanese garden, the secluded garden, the lilac garden - adding small but significant changes, such as mowing the grass to benefit butterflies - and adding whole departments such as the Centre for Economic Botany, showing politicians across the world how endangered plants are worth saving, for they may have valuable uses.
In retirement, he will be scientific director of the Eden Project, a millennium-funded recreation of the rainforest and other environments in Cornwall. He is happy with his successor, another mid-Atlantic man, Professor Peter Crane, an Englishman who comes from the Chicago Field Museum; he is happy with what he has done. But not as happy as those who have observed him closely.
"The value of Sir Ghillean's contribution to Kew's development, said the chairman of the Kew trustees, Lord Blakenham, "cannot be overstated."Reuse content