We begin with McDonald's. The nearer we get to a branch, the more people I notice who are tucking into tubs of McFlurry Caramels (99p). I decide to sample that as well as a Cone and Flake (59p). "The key to trying ice cream is 'mouth feel'," explains Beattie, as she thoughtfully licks her ice. "McDonald's ice creams have a fluffier, lighter mouth feel and a more delicate vanilla taste than your average Mr Whippy. They are designed to appeal to absolutely everyone by being so bland as to be inoffensive."
As her ice cream drips down its cone, Beattie points out how the mixture has separated, and now looks very watery. I dig into my Caramel McFlurry. It tastes as though a lot of caramel and milk chocolate chunks have just been tipped into the McDonald's ice cream; the sort of thing drunken flatmates mix together late at night when craving something very sweet and sickly.
Tracking down an ice-cream van willing to participate in our tasting proves more difficult. They are a secretive breed and don't want to be photographed, let alone written about - something about licensing, rivals and being stitched up by the press in the past. Consequently, I have to go undercover to sample my £1 Cornish Meadow cornet from a shiny red van I spot near Paddington Gardens. The Cornish Meadow has a classic, creamy, shaving-foam texture that coats the mouth with a plain, sweet, vanilla taste. It has a richer, creamier feel than the version from McDonald's.
Currently, anything sold as "ice cream" within the EU must contain a minimum of 5 per cent vegetable fat, such as coconut or palm oil, while anything sold as "dairy ice cream" must contain a minimum of 5 per cent cow's milk fat. After that, it is a matter of adding 2.5 per cent minimum of milk protein, along with sugar, or sugar and dextrose, emulsifiers, stabilisers and flavouring.
Time to visit Sarah Bartlett, pastry chef to the Michelin-starred Greenhouse restaurant. Much to my surprise, she uses stabilisers and an air-pumping "Paco jet" when making ice cream. "I can't imagine how people could operate without their Paco jet," says Bartlett with a laugh, as she thrusts a small jug of blueberry ice cream under the jet and swirls it around like a frozen cappuccino. The jet pumps air into the mix, making it almost as soft as a Mr Whippy, and easy to scoop into perfect quennelles.
"But why do you need stabilisers?" I query, thinking of a friend who has to rush to the lavatory if he consumes the smallest amount of guar gum. "We only use them in some of the ice creams," she replies. "MSK Silk or Tremoline, for example, gives sorbets and chocolate ice cream a really silky texture."
Beattie and I slip our teaspoons into Bartlett's jasmine ice cream. She has made it without eggs so that we can compare the texture with her egg-rich, custard-based Earl Grey ice cream. "Mmm, see how light and clean the jasmine tastes and feels," says Beattie, happily taking another spoonful. "The extra air gives you a creamier mouth feel, whereas the egg yolks in the Earl Grey give it a richer, less-clean flavour."
Bartlett, however, prefers ice cream made with a proper custard. "I think eggs give ice cream a richer taste and a smoother, more full-bodied texture; otherwise, it's a bit like making a lobster bisque without any cream," she says. We all (including the photographer) scrape the plate clean. A dessert plate of ice cream here would cost £10, although the Greenhouse normally serves ice cream as part of a pudding.
In a bid to search out some mass-produced premium-quality ice cream, we decide to head to Häagen-Dazs in Leicester Square. After all, it was Häagen-Dazs that made the British see ice cream as cool and sexy. The company arrived here from the US in 1988 and poured bucket-loads of money into market research and a massive advertising campaign. It highlighted the fact that its ice cream contained fresh cream, skimmed milk, sugar and fresh egg yolk with no stabilisers. These ensure that the texture of the ice cream doesn't change throughout its frozen lifespan (the egg yolks act as a stabiliser).
Beattie suggests that we start with vanilla (£2 per scoop), pointing out that this is Britain's best-selling ice-cream flavour. It is very rich and creamy, with a good, natural vanilla flavour, although a little too sweet for my taste. In fact, all the Häagen-Dazs ice-cream flavours that we try seem very sweet, no doubt since the company adheres to its original American recipes, which tend to be sweeter than traditional European ones. We then taste the pralines and cream, which Beattie explains revolutionised ice-cream flavouring when it was first introduced to Britain back in 1998, because Häagen-Dazs made it with then-unfamiliar pecan nuts.
Time for a rest, so we collapse on to the Inn the Park's shady verandah in St James's Park. Strictly speaking, we have come to sample a selection of the small tubs of Judes' "ice cream with soul" sold here (£2.50), as Judes is a new, small, English company. However, both the "very vanilla" and "chunky chocolate" prove distinctly soulless, with a sticky, cloying mouth feel. Not a patch on the mini-tubs of Hill Station's excellent (stabiliser- and emulsifier-free) ice cream sold at the London Eye (£1.90).
However, we are consoled with Jane Huffer's creations. She is pastry chef at the Atlantic Bar and Grill, and makes all the Inn the Park's scoopable ice cream, with no additives, emulsifiers or stabilisers. (Emulsifiers, in case you are wondering, are used to ensure that the fat and water remain bound together when mixed.) Huffer's "English apricot" ice cream (£2 per scoop) is, as Beattie puts it, "the mutt's nuts", with its creamy custard base and tart, sour-cream finish. Nor can we fault her strawberry sundae (£6), which we all demolish in minutes.
Refreshed, we head off for our final two ice-cream makers: Morelli's in Harrods and Oddono's, a new Italian artisan gelato-maker based in South Kensington. The Harrods branch of Morelli's is run by Gino Soldan. He is obsessed by ice cream and, as he enthusiastically tells us, is prepared to make it in any flavour. Some of his more bizarre commissions have been for "baked beans on toast" and "Marmite with pickled onion and white chocolate".
Gino whisks one ice cream after another under our noses with the air of a concerned artist. Opinions differ on the ices, some loving his "Ace" - orange, carrot and lemon sorbet (apparently a classic-pick-me up ice in Italy), while others prefer his aromatic, pale-green Aloe Vera ice (£2.25 per scoop).
"Although there is a lot of experimentation in ice-cream flavours," muses Beattie, "people still mainly go for the classic flavours, such as chocolate, hazelnut, vanilla, pistachio and strawberry". But, I think, what about mango, cardamom or even passion fruit with white chocolate? These are all flavours I have come across today yet, 10 years ago, they would have been regarded as too exotic.
By the time we reach Oddono's, even Beattie looks a bit ice-creamed out, so it is a relief to find that the tempting array of home-made sorbets and ice creams taste as good as they look. As we stand by the tiny counter, children and adults alike squeeze into the shop to select their favourite flavours - Valrhona chocolate, hazelnut, pistachio, followed by mango sorbet. It almost feels like Italy. One scoop here (costing £1.50) is the equivalent of two elsewhere.
Sitting outside and eating a lychee sorbet, I wonder if small artisan ice-cream shops could open across the country, in much the same way as coffee shops first did back in the 1990s. Wouldn't that be wonderful?
WHERE TO FIND THE ICE CREAM
The Greenhouse 27a Hays Mews, London W1X, tel: 020 7499 3331
The Ice Cream Alliance tel: 01332 203 333; www.ice-cream.org
Morelli's in Harrods 87-135 Brompton Road, London SW1, tel: 020 7730 1234; www.harrods.com
Oddono's 14 Bute Street, London SW7, tel: 020 7052 0732
Inn the Park tel: 020 7451 9999
Hill Station www.hillstation.co.uk