This week sees the announcement of an £18 million investment at Mortlach distillery on Speyside by its owner Diageo.

Built in 1823, Mortlach was the first distillery in the region's whisky capital of Dufftown and pre-dates its world-famous neighbour Glenfiddich by more than 60 years.

Very little Mortlach seeped out as a single malt, for almost every drop has disappeared into a blend. All that is set to change with the release of four new single malts and a doubling of the distillery's capacity by building a replica of the existing still house.

Nick Morgan, the former head of Diageo's single malts and now in charge of whisky outreach - whatever that means - is clearly excited. "My colleagues say it's the biggest thing we've done in malt whisky for a decade or more."

The firm's massive new malt distillery at Roseisle, near Elgin, and the one being built on the Cromarty Firth are there because of blends, and the boundless ambition of Johnnie Walker in particular. The Mortlach investment is about single malts, and aimed at what Morgan calls "the global, luxury connoisseur market". They won't be cheap, in other words.

With access to Diageo's entire drinks cupboard, one can imagine Morgan drinks nothing but the finest malts and looks down on blends as a sort of base camp for beginners on the road to spiritual enlightenment. Instead he leaps to the defence of blended Scotch. "I'm always astonished that single malts account for 5% or 6% of the business, but they gobble up around 94% of the conversation."

In most whisky books, my own included, the figure is usually higher with blends barely mentioned in the A to Z trawl through Scotland's malt distilleries, and maybe this is reassuring for whisky drinkers. In an uncertain world it is good to know that blends are good and malts are better - and this is reinforced by the prices charged in every shop and bar in the country. Added to which blends are bulked up with supposedly inferior grain whisky, and malts tend to be older.

Having recently tasted some fantastic single grain whiskies I'm not sure about the first point, while age doesn't necessarily signify quality either. The truth is not that simple, for there are some wonderfully beguiling blends out there, along with some single malts that should never have left the distillery.

One thing's for sure. Scratch beneath the surface of the industry and there is no demarcation dispute between the two styles of whisky. "Companies like Diageo," says Morgan, "seek to make the very best single malt whisky, be it Mortlach, Talisker, Lagavulin or the like, to produce blends. Everything we do is about blends."

Maybe not everything, but I see his point. It was the 19th-century blenders who dragged the whisky industry up by its boot straps. They not only introduced the world to Scotch, they demanded and got more consistent quality malt from the distillers too. Before long they were buying up the distilleries to form fully-integrated whisky companies. The problem with today's blends is the lack of choice. Yet this Christmas there's at least one newcomer in the shape of the new Black Bottle blend, whose rougher edges have been sanded down into something dangerously smooth.