It's beer o'clock on a Brussels daytrip

Padraig Gibbons points to the luggage rack above his head. We're on our way to Brussels for a whistle-stop tour of the city's beer highlights and he's brought a large, pull-along bag (the sort commonly used by elderly ladies for their shopping) to carry back bottles of beer. "I'm not messing around," he says, smiling.

Clearly not, and he's far from alone: there are 10 of us in carriage 3 of the 8.04am Eurostar service to Brussels and we're all here for the beer. Outside, the gentle, drizzle-drenched charm of the Flemish countryside passes by almost unnoticed as the trip's organiser, Tom South, a softly spoken Londoner who works at The Flying Pig, a craft-beer pub in East Dulwich, hands out copies of the day's itinerary.

It makes for a mouth-watering prospect. We will visit not only some of the best bars and beer shops that Brussels has to offer, but also Cantillon, one of the world's most revered breweries. While this tour has been organised by Tom – all of us know him through the Flying Pig, or a shared love for Crystal Palace Football Club – there are plenty of options for more organised tours, including Brussels Beer Tours, which follows a similar itinerary.

We arrive just after 11am. A brisk 10-minute walk from Brussels-Midi takes us to our first stop, Cantillon. It's a remarkable place: both a brewery and a museum. They've made lambic (a beer produced by spontaneous fermentation; the yeast that ferments the beer comes from the Brussels' air) here in much the same way for more than 100 years. Cantillon's beers are flinty-sour, complex and hugely fashionable with the world's beer cognoscenti.

As the others settle into their first glasses of the day, I wander off for a look around. The €7 entry fee, it soon becomes clear, is a bargain: strolling around unchallenged, I duck under brewing equipment and crane my neck to climb rickety wooden stairs.

It's at the top of such a set of stairs that I find a large, copper cooling tun, right in the attic of the building. On either side are slats in the walls, which allow airborne yeast to come into contact with the beer in the shallow vessel. It's a far cry from a mainstream brewery, where the idea of contamination keeps the head brewer up at night.

My interest sated, I make my way back downstairs to the brewery's bar, where the drinking has begun. Tom pours me a glass of 50°N-4°E, a cognac-barrel-aged special edition. A few yards away at the shop, Padraig is filling his bag with six bottles of Fou' Foune (the maximum he is allowed to buy), a much-coveted drop made with apricots.

The atmosphere in the group has transformed from anticipation into enthusiastic participation. Alan White, a 61-year-old south Londoner-turned-Devonite, smiles and calls across to Tom. "It's going to be like herding cats in a few hours!" he says.

Maybe even sooner. We empty our glasses and head for our next stop: Moeder Lambic, a bar on Place Fontainas. It's smart and sleek. I go for Cuvée De Ranke, an austere, lemony-dry pale ale.

Everyone has relaxed. The conversation moves on from beer, taking in rugby, music, modern Germany, the American political system. Across the table, the solitary American member of the party, Dina Slavensky, is tapping away at her mobile phone. Dina, a personal trainer who lives in Ealing, is updating her account on Untappd, an app that allows you to log the beers you've tried. She's 14 short of 1,000 and hopes to hit the big number in Brussels. A noble if, as it turns out, unrealistic goal.

At the next stop, a trinket-festooned bar called Poechenellekelder, close to the Manneken Pis, both Dina and I plump for a genuine world classic: an aged Orval. It's served in two glasses – a large one for most of the beer, a smaller one for the yeast-heavy liquid at the bottom – and it's tremendously good. There's a hint of sour (like Cantillon, it contains Brettanomyces, a wild yeast) and a candy-sugar sweetness. Together, they produce a drink of undeniable elegance. No wonder it's regarded by many as the world's greatest beer.

Another contender for that crown is waiting at De Biertempel, a shop close to the Grand-Place. The variety of Belgian beers on offer is startling, but one stands out: Westvleteren 12, a rarity regularly voted the best in the world. Despite the relatively hefty price tag (€9), I pop one in my basket. It'll be a reminder of the trip and a chance to see if the beer lives up to the hype, I tell myself.

Our backpacks bulging, we hurry on through incessant rain towards our next stop, a quirky bar-cum-puppet theatre called Toone. Most of the group go for Rochefort 10 (like Orval and Westvleteren, a Trappist ale); a cat wanders in, eying the group of soggy beer pilgrims with understandable suspicion.

Time is getting on and the final two stops pass in a blur. First, there's A la Mort Subite, where I sip on a Faro – a sweetened version of lambic that was once the drink of the Brussels working man – and take in one of the city's most elegant and historic bars. Not for long, though: soon we're off to Bier Circus, which has a good selection of more modern Belgian beers and an impressively grumpy barman. I accompany a large but rather expensive plate of moules-frites (€20) with a glass of the gently bitter, effervescent Saison Voisin.

Moules seen off, I'm nervously eyeing my watch – and, with less than a half an hour until our train leaves, we're soon standing outside waiting for a cab. It arrives and so do we, just in time. Later, as the train rushes under the Channel, Tom floats an idea. "I think we should do two days next year," he says. "Bruges and Brussels." Now that sounds like a plan.

Getting there

Will Hawkes travelled as a guest of Eurostar (08432 186 186; eurostar.com) which operates up to nine daily services from London St Pancras to Brussels with return fares from £69. Tickets to any Belgium station start from £79.

Drinking there

Cantillon, 56 Rue Gheude (00 32 2 521.49.28; cantillon.be). Free to visit for a drink; €7 for brewery tour, including a drink.

Moeder Lambic, 8 Place Fontainas and 68 Rue de Savoie (00 32 2 503 60 68; moederlambic.com).

Poechenellekelder, 5 Rue du Chêne (00 32 2 511 92 62; poechenellekelder.be).

Bier Tempel, 56 Grasmarkt (00 32 2 502 19 06; biertempel.be).

Toone, Impasse Sainte-Pétronille, 66 Rue Marché aux Herbes (00 32 2 511 71 37; toone.be).

A la Mort Subite, 7 Rue Montagne-aux-Herbes Potagères (00 32 2 513 13 18; alamortsubite.com).

Bier Circus, 57 Rue de l'Enseignement (00 32 2 218 00 34; bier-circus.be).

Brussels Beer Tours (brusselsbeertours.com) offers a three-and-a-half–hour tour of Brussels' beer highlights, including Cantillon. The tour costs €45, including five beers.

More information

visitbrussels.be