Big breweries, like oil tankers, take a long time to turn round. Greene King, based in Bury St Edmunds in Suffolk, is one of Britain’s biggest regional brewers. With 2,400 pubs, restaurants and hotels, it has – to use marketing jargon -- “national reach” and is best known for two of its cask beers, IPA and Abbot Ale.

For many years, IPA has been the subject of some criticism in beer-writing circles. There’s nothing wrong with the beer – it’s the biggest-selling standard real ale in the country and millions of satisfied drinkers can’t be wrong. The criticism centres on the brand name IPA: surely, the critics argue, a beer with a modest strength of 3.6% shouldn’t be called India Pale Ale.

The original IPAs from Victorian times were around 7 or 8%. They were first brewed for export to India where the Raj and British military personnel wanted a refreshing beer. High levels of alcohol were needed to keep the beer in good condition on long sea journeys to the sub-continent.

Nobody would argue today that all IPAs should mirror the levels of alcohol of the 19th century, but 3.6% is a tad on the low side.

Greene King listened to the critics and conducted a year-long survey into the preferences of more than 30,000 drinkers. The study found that while real ale sales are driven mainly by 35+ males, younger consumers are also switching to the category. Market share for cask beer among males aged 25 to 34 has grown to 19%.

Encouraged by this research, Greene King launched a £4 million promotion for IPA in the spring, with advertisements appearing on several TV channels. As part of the package, the brewery included two new versions of IPA called IPA Gold and IPA Reserve. At 4.1% and 5.4% respectively they are within shouting distance of the true India Pale Ale style.

Both Gold and Reserve are also available in bottle and all the versions of IPA can be found in most major supermarkets, including Asda, Morrisons, Sainsbury’s and Tesco. Gold, as the name suggests, is a pale beer with an aromatic nose and palate of tropical fruits, mango and spices due to the use of Savinsjki hops from Slovenia. It’s a quenching and fine tasting beer.

IPA Reserve is a superb ale. Greene King dates from 1799 and Reserve is based on a 1820s recipe. It has a deep, burnished copper colour from pale malt and darker grains, along with Styrian Goldings, another hop variety from Slovenia. The beer delivers grapefruit and orange notes alongside a rich biscuit malt character, followed by a dry and hoppy finish.

Not all the versions of IPA may be on bars at the same time but they’re worth seeking out in Greene King pubs in the area, including the Elephant & Castle in Amwell, near Wheathampstead, and the Speckled Hen on Hatfield Road. Free houses, including the Brocket Arms at Ayot St Lawrence and the Woodman at Wildhill, often feature the brewery’s beers.

Greene King is a brewery with history. Its most fascinating beer is called Strong Suffolk Ale, available only in bottle. It’s 6% and it recalls a method of brewing that dates from the 18th century when many brewers blended two types of beer. One version was called old or stock ale, which was matured for long periods in wooden vats called tuns.

Strong Suffolk is still made in this fashion. Tucked away at the back of the brewery’s fermenting rooms are three large, 60-barrel tuns that contain a beer called Old 5X. It’s 12% and it ages in the tuns for between one and two years. The wooden lids of the tuns are covered in sandy gravel known as marl: it prevents the lids lifting during fermentation and stops oxygen spoiling the beer.

As a result of this long ageing process, Old 5X has an oaky, slightly sour and pronounced port wine character. It’s blended with a 5% beer called BPA – short for Best Pale Ale. The result is a rich beer with a spicy, oaky and sherry aroma and palate, with some tannins, vanilla and caramel from the wood.

Enormous interest was created at the Great British Beer Festival in London in August when small samples of Old 5X were made available. But neither this beer nor BPA are usually sold separately as both are brewed for blending. Strong Suffolk is available in selected retail outlets or from www.greenekingshop.co.uk.

Bury St Edmunds, with its monastery ruins and fine Georgian buildings, is well worth a visit. Greene King has a visitor centre that’s open Monday to Saturday and brewery tours are available every day – including views of the Old 5X wooden tuns.

*Roger Protz is on Twitter @RogerProtzBeer. He edits the CAMRA Good Beer Guide.