Blow the budget: Randle Siddeley's 'Garden' reveals what to do with your green space if money were no object

Have you ever wondered what it would be like to be a billionaire, able to call in the world's snazziest garden designer? I've spent some hours on the bus pondering this question over the years, but now there's a definitive answer in the form of Randle Siddeley's Garden. This luxurious volume comes in at a mind-boggling 50 smackers – half a ton to you, mate – but for that price it does let the reader enjoy the fiction that they are perfectly at liberty to build an enormous swimming pool in a room underneath their lawn, or put a quick Rodin down the end of the grand allée, should they so wish.

In fact, as Siddeley's book reveals, the clients' wishes may not always be the exact starting point. In one Cotswold project he was initially invited to propose planting for the area around the house. Siddeley saw the site and immediately thought up something bigger. Result? A four-year earth-moving project to level a hillside, making two acres of level garden for dining area, rose plantings and swimming pool. A mammoth project, not even remotely what I'd do, and strangely addictive reading.

Spending imaginary money does take some thought. For example, when we are billionaires, our privacy will, of course, be of huge concern. But never fear: Siddeley has a knack for figuring out what to do with that pesky public footpath overlooking the house (not removable, by any amount of legal manoeuvring? Call in the bulldozers and lower it out of sight) and that staff cottage (the staff actually want some outdoor space for their children? OK, then, hide it behind a gigantic bronze pool).

Yet, daydreaming aside, is there anything that gardening on this scale can teach us normal mortal gardeners? The book has useful thoughts about how outdoor space needs to work. A kids' trampoline is fitted into a hole, leaving it neatly at lawn level, drastically reducing the accident risk. Want a patch of grass, despite the shade in your garden? Annual returfing might be more satisfactory than struggling on, scrappily. And a bench at the side of a parking area softens the look of the hard landscaping, but also gives somewhere to rest shopping bags while unloading the car. Whether or not they are Hermés, this still seems a nice idea.

And if you would rather hold on to your Monopoly money, in a timely coincidence Noel Kingsbury has just published Garden Designers at Home: The Private Spaces of the World's Leading Designers. Forget seeing what the super-rich are up to: this way you can nick the horticultural tips of those big-brained individuals who think up the schemes to start with. There are some surprising revelations. Penelope Hobhouse, a green-fingered grande dame, retired to a small coach house in 1993, yet the garden she made there is startlingly modern with a delicious sky pool viewed through uninterrupted glass. And Tom Stuart-Smith, Chelsea big cheese and champion of the very restrained, turns out to have a girlishly abundant garden at home, full of romping roses. I'll leave you to grab a copy of the book and ponder over which you prefer.

'Garden', by Randle Siddeley, is published by Frances Lincoln, priced £50. 'Garden Designers at Home', by Noel Kingsbury, is published by Pavilion, priced £25

Visit the designers' gardens

The great

The Bannermans

are British garden design's golden couple, and their own house, Hanham Court, near Bath, is currently for sale, so see it while you can. Towering topiary and softest flower planting, all to chocolate-box effect. Sunday and Monday afternoons only, 2.30pm-5pm, to 8 August. hanhamcourt.co.uk

The gaudy

John Brookes' garden at Denmans, West Sussex, is a real treat for those of us who grew up on his seminal book Room Outside. Open 9.30am-5pm all year round, it has a wonderful series of staged views, unusual plants and deliciously gaudy colour combinations. denmans-garden.co.uk

The blissful

Tom Stuart-Smith's family garden is open on 19 June for the National Gardens Scheme, along with one other in Serge Hill, Herts. Home-made teas will be the least of the attractions as you get to nose around this blissful garden. £6 admission. ngs.org.uk