An email from Rupert Ponsonby, Cotswold farmer, beer-enthusiast and founder of the PR company R&R Teamwork, usually contains an invitation I simply can’t refuse.

It was Rupert who arranged for me to take an air balloon trip with a food scientist while sipping champagne and deciding if the bubbles really did get bigger as we floated over the Cotswold hills. Several years ago he organised a coach trip around some of the top London restaurants, each of which served us with a different course to eat while travelling to the next establishment. The idea was to match each dish with a beer and decide if food eaten when travelling through the London lights was enhanced by the experience. He has arranged chocolate and beer tastings, too, and once staged a picnic in an Oxfordshire wheat field which included a trip to an Oxfordshire hop farm.

A pork scratchings pub crawl around Oxford was great fun, but when Rupert invited me and several other food writers on a trip to Yugoslavia for lunch,this proved so comic that it got mentioned in the national press. Those on that trip still smile when they talk about that day and recall the moment we all realised we were not going to get back to the UK in time for dinner.

The email that arrived last month invited me to a “Hop Rubbing session” on a hop farm in Worcestershire. Having never attended a hop rubbing session, there was no way I could refuse, particularly as the event was arranged to launch Marston’s 12 single hop varietal ales, which will be brewed every month during 2012. Some will be brewed with hops never seen in the UK before. The concept for this exciting range comes from a desire to satisfy customer hunger for different taste experiences, allowing pub drinkers the opportunity to understand how ingredients such as hops influence the flavour of beer, while providing a talking point revolving around cask ales. Grape varieties are taken seriously by wine drinkers, so why not let hop varieties enjoy the limelight too? By using just one hop variety in a brew, we get a chance to see exactly what it offers.

Marston’s programme will offer different carefully selected four per cent ABV brews every month during 2012, each brewed to the same basic recipe a different hop variety.

Marston’s category manager, Ian Ward, who attended the hop rubbing, said: “Hops are the herbs and spices of beer and each hop has its own flavour and fragrance — they impart their unique character in a manner similar to grapes in wine. Most beers call for a mixture of hops, so by producing an ale from a single hop variety we are allowing drinkers to understand what makes flavour and how it works.”

So there we all were sitting round the large kitchen table at Charles Faram’s beautiful old farmhouse, rubbing hops to release their fragrance, while trying to decide the distinct aromas we could detect. One of the most fascinating things that came out of this exercise was the fact we all detected different scents, just as we would have done during a wine tasting. Take the Wai-Iti for example. This is a new hop variety from New Zealand. I thought it had a strong citrus aroma, whereas others identified a mild fragrance of passion fruit. As this hop variety is still undergoing trials there is no published information available for its oil or flavour profile yet, so any one of us could have been right.

Then there’s Galaxy, from Victoria, Australia, and Tasmania. This is also an exciting new cultivar with striking flavours which include a hint of peaches. The English hop East Anglian Golding was included. Goldings are the most quintessential of English hops having been grown in Kent for more than 200 years. This hop provides an earthy bitterness with hints of spice, which most of us appeared to identify correctly during the rubbing. This is the hop from which classic British bitters are brewed.

All hops will be sourced through Hop Merchant and hop farmer Charles Faram whose farm we were visiting. This farm stocks and sells the largest range of hops in the UK, offering more than 50 varieties, from the traditional Fuggles and Goldings to the more distinctive citrus of Pioneer or the delicate European floral age flavour of Hersbrucker. As we were visiting during the winter, we were unable to see the hop vines in full bloom, just rows and rows of carefully-pruned hops awaiting the moment spring arrives and they can burst into life again. It was nevertheless a fascinating experience.

Each month Marston’s chief brewer will blog details of the month’s brew on the Marston’s website (www.singlehops.co.uk).