Near the picturesque village of Caldbeck in the Lake District, engineers have started work on what will be the third-highest structure in Britain — a 337-metre (1,106ft) television mast that will be used to transmit digital television programmes to the Border region.

The new mast is evidence of the gathering momentum behind the government’s plan to embrace the digital broadcasting revolution. Over the next six years, some 5,000 analogue — or old-style — transmitters will be replaced by new and more efficient digital equipment.

Switching off the analogue services will release a sizeable block of prime radio spectrum — 14 channels in the ultra-high frequency band. The question is: who will get to use them? The competition pits broadcasters such as the BBC against mobile-phone firms and new wireless broadband services. The power to award licences and therefore shape the future of broadcasting lies with the telecoms regulator Ofcom.

It sounds like an arcane decision, but it is not. Ofcom’s ruling could potentially bring in billions of pounds of revenue to the government. And already big commercial interests are at play, with companies jockeying for position in order to stake their claim for a lucrative slice of the airwaves.

There are also class and age issues at stake that will sorely exercise the minds of watching politicians.

Put at its crudest, the regulator must decide what is better: to allow millions of teenagers to watch Big Brother on their mobiles, or to let Grandad watch the 2012 Olympics in glorious high definition?

For many people the digital television era has already arrived. More than 70% of British homes watch digital television on Freeview, Sky or the cable company NTL. (BSkyB, the satellite broadcaster, is 37.7% owned by News Corporation, ultimate owner of The Sunday Times.)

However, the limitations of the existing infrastructure mean that a quarter of UK households are unable to receive digital programmes through roof-top aerials. The £500m upgrade that began last month will boost transmission signals so that Freeview — the “terrestrial” version of digital TV — can be enjoyed by almost the entire nation.

To date, much of the debate over the switch to digital has centred on the political risks. From 2008, analogue transmitters will be successively switched off, the process starting with the Border region and completing in 2012 with London, southeast England and Northern Ireland.

The fear is that many elderly, poor and otherwise disadvantaged viewers could be left behind — and denied access to the familiar BBC and ITV channels that are their window on the world.

The latest BBC advertising campaign, featuring Peter Snow, Bill Oddie and Penelope Keith, is only one of many public-information initiatives intended to explain the benefits and challenges of digital television.

BUT behind the scenes the commercial dispute is already brewing over who will get the sizeable block of spectrum that will be made available when analogue is switched off.

This spectrum, dubbed the digital dividend, could be put to many uses for the benefit of consumers and businesses. But who gets to use it, and how, has yet to be decided.

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