Although a relative newcomer, Magners has already claimed packaged cider's top spot in the on-trade, with 30.6% market share
Undoubtedly the strongest challenge to Strongbow in recent times hasn't come from its traditional rivals in the West Country, but from across the Irish Sea.
Magners is a UK incarnation of the Bulmers cider brand in Ireland. Ironically, brand owner Cantrell & Cochrane couldn't use the name Bulmers in the UK because the trademark is registered with Scottish Courage since its acquisition of Bulmers and Strongbow.
Magners has built up an enthusiastic following in Scotland on the back of a marketing campaign suggesting it should be served over ice.
It's now rolling out in London and south-east England with a heavyweight advertising campaign, although it's arguably punching above its weight in terms of PR voice against actual sales or distribution.
Stephen Kent, marketing manager for William Magner, said: 'We had an initial base built up with Irish pubs in the south of England and that gave us something to build on. Along with that, there's just been a lot of honest endeavour by the sales team to get distribution and awareness to drive it through.
Already it's proved enough of a thorn in Strongbow's side for Scottish Courage to launch its own over-ice premium brand, Sirrus.
But Kent says the brand is aiming to steal drinkers from other categories too.
'Even though there are 29 other ciders on the market in Ireland, we see ourselves as competing on a much wider footing than just cider, he says. 'While obviously we'll be going up against Strongbow and Blackthorn, we see ourselves as competing much wider than that.
The Magners effect has received almost universal acclaim in the industry and so far its success has been built on the back of limited geographical distribution.
It's already the number one packaged cider in the on-trade with 30.6% market share in the year to March, according to AC Nielsen. A year earlier that figure was just 3.7%.
AC Nielsen's Sukhvinder Gill says: 'When its distribution is rolled out you can only imagine that it will go from strength to strength.
At the moment it's only possible to speculate on what impact it might have if it was launched on draught.
John Edwards, on-trade sales manager for rival Westons Cider, says: 'Magners has brought a different concept to cider and it's worked well for them. They've obviously got a strong marketing background and big percentage of business in Ireland already. But it's captured people's imagination and any advertising or marketing has got to be good for the sector as a whole. It's got people looking at cider from a different perspective.
Westons itself has made good progress with Stowford Press, which has become the cider brand of choice for outlets ranging from top-end independent style bars to country freehouses.
Edwards says: 'I think people like the fact that we have very high quality and tradition. We use locally-grown fruit and we don't compromise on that. We also don't totally rely solely on keg or on bottles for take-home as some companies do, so we aren't reliant on one sector of the market.
'We know Stowford Press is very versatile. It can't be described as particularly sweet or particularly dry. It's down the medium route, which has a wider appeal. One of the most common comments we get is that it reminds people of how cider used to taste. It's a very credible alternative to have on the bar.
But although winning lots of friends, Stowford Press is still way short of Strongbow's lead. According to CGA-Centro data for March 2005, the market leader has 62% distribution. Stowford Press is one of a clutch of recognisable brands with just 1% penetration.
Another of these is Addlestones, Gaymer Cider's cask-conditioned brand. The company is preparing to inject some new life into the brand, perhaps mindful that Blackthorn could be metaphorically banging its head against a brick wall in a mainstream head-to-head with Strongbow. Blackthorn's own distribution is just 16%, around a quarter of the category leader's.
Gaymer is targeting a new-look Addlestones with a minimalist font at real ale pubs and style bars, with a number of the latter currently trialling this.
Gaymer's spokesman Simon Russell said: 'There is an opportunity for specialist and premium ciders like Addlestones. In style bar outlets, the taste profile and the slightly cloudy appearance of Addlestones appeals to consumers searching for something interesting and different.