Todd Longstaffe-Gowan insists history is not a "crutch" but a source of great inspiration to inform and motivate creativity. He has a £1.2m budget and with it will wrench up railings, fell trees and sweep away clutter to open up vistas and axes.
"It's extraordinary, as good as Stowe or Blenheim but in the middle of the city," he says. "Much of the original fabric of alleys, earthworks and water remains and we are using the history of the garden to inform us. The idea of immensity is compelling."
And he will not shy away from immense decisions. When he tackled Hampton Court, an avenue of trees had to go. Oh, the controversy - but when he explained his rationale and that visitors would see views last enjoyed by Charles II, opposition melted.
If only other designers had such clarity of vision as Longstaffe-Gowan, who hates the label "landscape architect". Landscape architects more generally have been woefully unresponsive to the needs of today's open spaces and lacking in design subtlety.
"So many landscape architects are ghastly and inept," he says. "I much prefer to call a garden a garden. Most landscapes are over-elaborate and over- prescriptive. I am trying to strip away rather than add too much; make things more visible and flexible.
"I consider my role as a steward, not strictly a designer. I have a responsibility to sustain the fabric, keep vistas open and build on the existing legacy of the past with improvements. I'm certainly not driven to create great monuments to my own work. Often the simplest solutions are the most eloquent. Yet there's a tendency in our profession to overcomplicate with too many paving surfaces or elaborate flourishes. Hyde Park is such a noble, simple landscape because it is trees and grass."
Working with the Royal Parks is a dream for Longstaffe-Gowan, who runs his practice, Landscape Design, on the fourth floor of an open-plan office in east London shared with fellow big-name designers Jinny Blom and Tom Stuart-Smith. Three illustrious creative minds under one roof is "all very congenial", he insists. All are good friends and bounce ideas off each other with no sense of competition. Longstaffe-Gowan's practice is nevertheless "unusual", he says.
A glimpse at his Mile End home, Malplaquet House, hints at the unusual nature of Longstaffe-Gowan's professional approach and more general outlook. Limewashed rooms backdrop taxidermy, architectural salvage and oddities like an ostrich skeleton.
"I'm not interested in large, commercial landscapes and enjoy working with clients rather than big corporate bodies," he says. "I like life close to the coalface and enjoy one-to-one interaction. The Royal Parks are wonderful because they care so much."
Longstaffe-Gowan was born in Canada and grew up in eight countries, including the West Indies. Academic stints at Harvard, Yale, University College London and the Getty Research Institute, in Los Angeles, led to work in Greece, France, Italy and Spain.
"By keeping an academic face I'm trying to promote a broader appreciation of landscape," he says. "It's so easy to get worn down by the nuts and bolts of professional matters and lose sight of creating wonderful places."
He also writes books on historic gardens. Writing, he insists "congeals your thoughts" and his latest, unfinished work focuses on a landscape feature that sums up so much of what's so wrong with landscape design in the 21st century, he reckons.
The strength in simplicity of the historic square in the public domain has been lost in a welter of designated areas for children and dogs, bins and fencing, he says. This diminishes the impact of a simple expression and ruins the whole composition. "I would like to see more collaboration between tree officers and conservation officers so all landscape expressions in towns are much more coordinated. Conservation officers are interested in the fabric of the houses, rarely the square itself.
"We have horrible desecrations because landscape is never treated with the same respect as the buildings. There's no coherent vision on how it ought to be appreciated. Squares are one of the greatest urban forms of the 17th century, but are undervalued."
Kensington Palace Gardens, he says, will not go the same way as the squares. "This is a big job for a small office, but there's enough legacy to inform. I feel the experience can be humbling," he says, quoting Oscar Wilde's phrase that "ambition is the last refuge of failure".
"You are part of the continuum, not a monument. I'm one of several gardeners throughout the centuries to make small improvements. I like being part of a sequence of people; you have a role but know other people will come and do other things."
1978-1998 Degree in architecture, followed by a Master's degree in landscape architecture and a PhD in historical geography. Works for Elizabeth Banks and co-founds the London Parks & Gardens Trust
2000-2004 Sets up landscape practice in London and writes The London Town Garden and The Gardens and Parks at Hampton Court Palace
2008-2012 Appointed to landscape Kensington Palace Gardens after successful projects at Trentham Gardens, Waddesdon Manor and Southwark Cathedral