My hidden hero: Emma Townshend gets a tour of James Alexander-Sinclair's secret garden

In a recent list of Britain's top 10 garden designers compiled by Annie Gatti, the co-author of The Good Gardens Guide, James Alexander-Sinclair was notable by his absence. Perhaps that's because it's so hard to see his gardens, which are too often private beauties tucked away in secret country places. (Cottesbrooke Hall in Northamptonshire is a good exception, and is open to the public until September on Thursday afternoons.)

Famous for giving gardening advice with a touch of PG Wodehouse humour and a shot of raffish glamour, Alexander-Sinclair is beloved by most of his peersfor television shows such as Small Town Gardens and the regular column he writes for Gardeners' World magazine, in which he catalogues in elegant prose the best floral treats in store each month.

Now those Gardeners' World columns have been turned into a useful reference book, small yet packing a powerful floral punch. Called 101 Bold and Beautiful Flowers, it's the kind of book you take to read in the bath, then, because the writing is so seductive and the recommendations so tempting, you find yourself with horrible wrinkly skin still reading an hour later.

Given his hero status in my household, I was happy to have secured an invite for myself to morning coffee at Blackpitts in Towcester, Northamptonshire – Alexander-Sinclair's own garden, which features in his witty and lushly illustrated blog. It's always an intriguing experience when you first glimpse the garden of someone you like. What will it tell you about them that you didn't know? (Your well-turned-out colleague with the immaculate desk whose relaxed approach to their flowerbeds hints at unanticipated levels of mental disorder, for instance.)

At Blackpitts, I wasn't surprised to fall in love with the plants; I knew they'd be a treat given Alexander-Sinclair's past form. The surprise was the garden's unexpectedly strong backbone and the way the structure of the space works: containing movement without dictating it.

In a home awash with teenagers and dogs, I'm amazed he gets away with this elegant design. But it's a real-life garden that must work for other members of the household, too. "The beech pillars do get used for goalposts. And they make croquet a lot more interesting," he laughs ruefully.

If I won the Lottery, it's him I'd be calling in. And not just for the gossip and cake. n

For more information on Cottesbrooke Hall, visit www.cottesbrookehall.co.uk. '101 Bold and Beautiful Flowers' (BBC Books, £4.99) is out now. For more about Blackpitts and to read Alexander-Sinclair's blog, visit www.blackpitts.co.uk

Read Emma Townshend's new column at blogs.independent.co.uk/independent/a_nice_green_leaf

James's favourite flowers: Beautiful blooms for a late-summer effect

Cirsium heterophyllum

The "Melancholy" thistle has soft purple tops on elegant acanthus-like cups. The leaves are softer than most other thistles. Hardy's Cottage Plants, £7.50, www.hardys-plants.co.uk

Sanguisorba canadensis

A gorgeous tall white flower. James is a one-man sanguisorba publicity

machine; the best in his collection come from Marina Christopher at Phoenix Perennials (tel: 01420 560 695)

Rudbeckia 'Herbstonne'

Rather than the standard Rudbeckia brown, this has a green cone-like centre, which gives it a zingy effect. £3.60 from Beth Chatto, www.bethchattoshop.co.uk/shop