I was at an impromptu soirée in a loft on the Bowery. Johnnie Johnson was there, with his quintet, and the evening (as it inevitably does in New York) turned to jazz. Johnnie encouraged the guests to chat quietly and to "clink crystal" in order to add ambience to his vibe. But then, in lounge circles, Martini glasses are nigh-on a musical instrument. So I sank a few, and joined in on the bongos.

That was my last Martini. Until I found myself in the Long Bar at the Sanderson hotel. And boy, was that bar long! My normal instruction to friends ("I'll meet you at the bar") just wasn't specific enough. I should have given map references. But the surroundings were so elegant – all diaphanous fabrics, with the sort of furniture they have in heaven – that I decided to order up a lavender Martini.

Not the most masculine drink I've ever had. But one of the tastiest. The blend of flavoured vodka and flower liqueurs really worked. I'm not sure it was a proper Martini. I have one friend who makes his Martini dry to the point of absurdity, even recommending you make it without any vermouth at all. Call me old-fashioned, but if it doesn't have vermouth, it's not a Martini – it's just gin in a jaunty glass.

I have lived through the proliferation of "Martini menus". I have seen clubs claiming to serve 2,000 different types. But a "Martini" is gin and dry vermouth, garnished with olives or a twist, served in a cocktail glass. Heck, if you so much as change the garnish to a pearl onion, it ceases to be a Martini. It gets an entirely different name – a Gibson. So how can it weather the changing of its principal ingredients?

At least with the lavender, I didn't have to specify shaken or stirred. The myth persists that shaking instead of stirring a Martini somehow "bruises" the gin. Nonsense. In my leather-bound volume of mixology, there is no rule over when to stir and when to shake. So I penned my own. Take this down, young 'un: if the beverage contains only clear ingredients, stir. If it contains lemon, lime or an opaque cordial, then by all means shake. Whatever you do, it won't end up clear.

Bond is to blame. His Martini always marked him out as a man with upper-class sensibilities. The fact that he preferred it in such a "radical" way endowed his character with flair. I think Bond would have been man enough to order a lavender Martini. But then the double-0 appellation – the licence to kill – means your masculinity rarely gets called into question. E

The Long Bar, Sanderson, 50 Berners Street, London W1 (020-7300 1444). A proportion of money raised by the sale of lavender Martinis will go to the Lavender Trust, a charity set up to help young people affected by breast cancer (www.lavendertrust.org.uk).

You can e-mail Richard Johnson at drinkwithrichardjohnson@yahoo.co.uk